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1000 or one thousand is the
natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and total order, ordering (as in "this is the ''third'' largest city in the country"). In common mathematical terminology, w ...
following
999999 or triple nine most often refers to: * 999 (emergency telephone number) 250px, A sign on a beach in the coastguard in the event of an emergency 999 is an official emergency telephone number in a number of countries which allows the caller to ...
and preceding
1001 Year 1001 ( MI) was a common year starting on Wednesday A common year starting on Wednesday is any non-leap year A leap year (also known as an intercalary year or wikt:bissextile, bissextile year) is a calendar year that contains an additional da ...
. In most
English-speaking countries
English-speaking countries
, it is often written with a comma separating the thousands unit: 1,000. It may also be described as the short thousand in historical discussion of medieval contexts where it might be confused with the
Germanic Germanic may refer to: * Germanic peoples, an ethno-linguistic group identified by their use of the Germanic languages ** List of ancient Germanic peoples and tribes * Germanic languages :* Proto-Germanic language, a reconstructed proto-language of ...

Germanic
concept of the "
long thousand Long may refer to: Places * Long, Somme, a commune in northern France * Long, Washington, a community in the United States * Long District, Laos * Long District, Phrae, Thailand * The River Long, or Longjiang (disambiguation), Longjiang (literally ...
" (1200). A period of 1,000 years is sometimes termed, after the Greek root, a chiliad. A chiliad of other objects means 1,000 of them.


Notation

* The decimal representation for one thousand is ** 1000—a
one 1 (one, also called unit, and unity) is a number A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can ...

one
followed by three
zeros
zeros
, in the general notation ; ** 1 × 103—in
engineering notation Engineering notation or engineering form is a version of scientific notation in which the exponent of ten must be divisible by three (i.e., they are powers of a thousand, but written as, for example, 106 instead of 10002). As an alternative to writi ...
, which for this number coincides with : ** 1 × 103 exactly—in scientific normalized exponential notation ; ** 1 E+3 exactly—in scientific E notation. * The
SI prefix The International System of Units, known by the international abbreviation SI in all languages and sometimes Pleonasm#Acronyms_and_initialisms, pleonastically as the SI system, is the modern form of the metric system and the world's most wi ...
for a thousand units is "
kilo- Kilo is a decimal prefix, decimal metric prefix, unit prefix in the metric system denoting multiplication by one thousand (103). It is used in the International System of Units, where it has the symbol k, in lower case. The prefix ''kilo'' is der ...
", abbreviated to "k"—for instance, a kilometre or "km" is a thousand metres. * In the SI writing style, a non-breaking space can be used as a
thousands separator A decimal separator is a symbol used to separate the integer An integer (from the Latin wikt:integer#Latin, ''integer'' meaning "whole") is colloquially defined as a number that can be written without a Fraction (mathematics), fractional ...

thousands separator
, i.e., to separate the digits of a number at every power of 1000. * Multiples of thousands are occasionally represented by replacing their last three zeros with the letter "K": for instance, writing "$30K" for $30 000, or denoting the
Y2K The Year 2000 problem, also known as the Y2K problem, Millennium bug, Y2K bug, Y2K glitch or Y2K error, refers to potential computer errors related to the formatting and storage of calendar data for dates in and after the year 2000 200 ...

Y2K
computer bug of the year 2000. * A thousand units of
currency A currency, "in circulation", from la, currens, -entis, literally meaning "running" or "traversing" in the most specific sense is money Money is any item or verifiable record that is generally accepted as payment for goods and services ...

currency
, especially
dollar Dollar is the name of more than 20 currencies A currency, "in circulation", from la, currens, -entis, literally meaning "running" or "traversing" in the most specific sense is money Image:National-Debt-Gillray.jpeg, In a 1786 James Gi ...

dollar
s or
pound Pound or Pounds may refer to: Units * Pound (currency) A pound is any of various units of currency A currency, "in circulation", from la, currens, -entis, literally meaning "running" or "traversing" in the most specific sense is money Im ...
s, are colloquially called a ''grand''. In the United States of America this is sometimes abbreviated with a "G" suffix. * The factors of 1000 are: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, and 1000.


Properties

* 1000 is a
Harshad number In mathematics, a harshad number (or Niven number) in a given number base is an integer that is divisible by the digit sum, sum of its digits when written in that base. Harshad numbers in base are also known as -harshad (or -Niven) numbers. Harsha ...
in base 10. * The sum of
Euler's totient function In number theory Number theory (or arithmetic or higher arithmetic in older usage) is a branch of devoted primarily to the study of the s and . German mathematician (1777–1855) said, "Mathematics is the queen of the sciences—and numbe ...
over the first 57 integers is 1000.
Prime Curios!
mentions that 1000 is the smallest number that generates three primes in the fastest way possible by concatenation of decremented numbers (1 000 999, 1 000 999 998 997, and 1 000 999 998 997 996 995 994 993 are prime). The criterion excludes counting the number itself.


Selected numbers in the range 1001–1999


1001 to 1099

:
1001 Year 1001 ( MI) was a common year starting on Wednesday A common year starting on Wednesday is any non-leap year A leap year (also known as an intercalary year or wikt:bissextile, bissextile year) is a calendar year that contains an additional da ...
sphenic numberIn number theory, a sphenic number (from grc, σφήνα, 'wedge') is a positive integer that is the product of three distinct prime number A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), pr ...
(7 × 11 × 13),
pentagonal number 181px, A visual representation of the first six pentagonal numbers A pentagonal number is a figurate number that extends the concept of triangular number, triangular and square numbers to the pentagon, but, unlike the first two, the patterns involv ...

pentagonal number
,
pentatope number A pentatope number is a number in the fifth cell of any row of Pascal's triangle starting with the 5-term row , either from left to right or from right to left. The first few numbers of this kind are: : 1 (number), 1, 5 (number), 5, 15 (number), ...
:1002 – sphenic number,
Mertens function Mertens function to n=10,000,000 In number theory, the Mertens function is defined for all positive integers ''n'' as :M(n) = \sum_^n \mu(k) where μ(k) is the Möbius function. The function is named in honour of Franz Mertens. This definition ...

Mertens function
zero,
abundant number In number theory, an abundant number or excessive number is a number that is smaller than the sum of its proper divisors. The integer 12 is the first abundant number. Its proper divisors are 1, 2, 3, 4 and 6 for a total of 16. The amount by which ...
:1004 –
heptanacci numberIn mathematics, the Fibonacci numbers form a sequence defined recursion, recursively by: :F_n = \begin 0 & n = 0 \\ 1 & n = 1 \\ F_ + F_ & n > 1 \end That is, after two starting values, each number is the sum of the two preceding numbers. The Fibon ...
:1005 – Mertens function zero :1008 – divisible by the number of primes below it :1009 – smallest four-digit
prime A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime ...
,
palindromic A palindrome is a word, number A number is a mathematical object A mathematical object is an abstract concept arising in mathematics. In the usual language of mathematics, an ''object'' is anything that has been (or could be) formally defined, ...
in bases 11, 15, 19, 24 and 28: (83811, 47415, 2F219, 1I124, 18128) :1010 – Mertens function zero :1011 – The largest number that 2n contains 101 and doesn't contain 11011, and it is a
Harshad number In mathematics, a harshad number (or Niven number) in a given number base is an integer that is divisible by the digit sum, sum of its digits when written in that base. Harshad numbers in base are also known as -harshad (or -Niven) numbers. Harsha ...
in bases 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 (and 202 other bases). :1013 –
Sophie Germain prime In number theory, a prime number ''p'' is a Sophie Germain prime if 2''p'' + 1 is also prime. The number 2''p'' + 1 associated with a Sophie Germain prime is called a safe prime. For example, 11 is a Sophie Germain prime and 2&t ...
,
centered square number In elementary number theory, a centered square number is a centered polygonal number, centered figurate number that gives the number of dots in a Square (geometry), square with a dot in the center and all other dots surrounding the center dot i ...
, Mertens function zero :1014 – Mertens function zero :1015 –
square pyramidal number In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

square pyramidal number
:1016 – member of the Mian–Chowla sequence, stella octangula number :1018 – Mertens function zero :1019 –
Sophie Germain prime In number theory, a prime number ''p'' is a Sophie Germain prime if 2''p'' + 1 is also prime. The number 2''p'' + 1 associated with a Sophie Germain prime is called a safe prime. For example, 11 is a Sophie Germain prime and 2&t ...
,
safe prime In number theory, a prime number A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composit ...
:1020 – polydivisible number :1022 –
Friedman numberA Friedman number is an integer An integer (from the Latin wikt:integer#Latin, ''integer'' meaning "whole") is colloquially defined as a number that can be written without a Fraction (mathematics), fractional component. For example, 21, 4, 0, an ...
:1023 – the highest number one can count to on one's fingers using binary; also the magic number used in
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government The federal government of the United States (U.S. federal government or U.S. governme ...
signals. : 1024 – 210, the number of
byte The byte is a unit of digital information that most commonly consists of eight bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It ...
s in a
kilobyte The kilobyte is a multiple of the unit byte The byte is a unit of digital information that most commonly consists of eight bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, bene ...
(in 1999, the
IECIEC may refer to: Businesses and organisations * International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organizati ...
coined
kibibyte The byte is a unit of digital information that most commonly consists of eight bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. I ...
to use for 1024 with kilobyte being 1000, but this convention has not been widely adopted). :1027 – sum of the squares of the first eight primes; can be written from base 2 to base 18 using only the digits 0 to 9. :1028 – sum of totient function for first 58 integers; can be written from base 2 to base 18 using only the digits 0 to 9. :1029 – can be written from base 2 to base 18 using only the digits 0 to 9. :1031 – exponent and number of ones for the largest proven base-10
repunit prime In recreational mathematics, a repunit is a number like 11, 111, or 1111 that contains only the digit 1 — a more specific type of repdigit. The term stands for repeated unit and was coined in 1966 by Albert H. Beiler in his book ''Recreatio ...
,
Sophie Germain prime In number theory, a prime number ''p'' is a Sophie Germain prime if 2''p'' + 1 is also prime. The number 2''p'' + 1 associated with a Sophie Germain prime is called a safe prime. For example, 11 is a Sophie Germain prime and 2&t ...
, super-prime :1033 – locale ID of English (United States) in (some version of)
Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary {{Short pages monitor