6 (six) is the
natural number
In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...
following
5 and preceding
7. It is a
composite number
A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Accordingly it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime numb ...
and the smallest
perfect number
In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfec ...
.
In mathematics
A six-sided
polygon is a
hexagon,
one of the three
regular polygons capable of
tiling the plane. A hexagon also has 6
edges as well as 6
internal and external angles.
6 is the second smallest
composite number
A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Accordingly it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime numb ...
.
It is also the first number that is the sum of its proper divisors, making it the smallest
perfect number
In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfec ...
. It is also the only perfect number that doesn't have a
digital root of 1. 6 is the first
unitary perfect number, since it is the sum of its positive proper
unitary divisors, without including itself. Only five such numbers are known to exist. 6 is the largest of the four
all-Harshad numbers.
6 is the 2nd
superior highly composite number, the 2nd
colossally abundant number, the 3rd
triangular number, the 4th
highly composite number, a
pronic number, a
congruent number, a
harmonic divisor number, and a
semiprime. 6 is also the first
Granville number, or
-perfect number. A
Golomb ruler of length 6 is a "perfect ruler".
The
six exponentials theorem guarantees that under certain conditions one of a set of six exponentials is
transcendental. The smallest non-
abelian group is the
symmetric group
In abstract algebra, the symmetric group defined over any set is the group whose elements are all the bijections from the set to itself, and whose group operation is the composition of functions. In particular, the finite symmetric grou ...
which has
3! = 6 elements.
6 the answer to the two-dimensional
kissing number problem.

A
cube has 6
faces. A
tetrahedron
In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...
has 6
edges. In
four dimensions, there are a total of six
convex regular polytopes.
In the
classification of finite simple groups, twenty of twenty-six
sporadic groups in the
happy family are part of three families of groups which divide the order of the
friendly giant, the largest sporadic group: five ''first generation''
Mathieu groups, seven ''second generation''
subquotients of the
Leech lattice, and eight ''third generation''
subgroup
In group theory, a branch of mathematics, a subset of a group G is a subgroup of G if the members of that subset form a group with respect to the group operation in G.
Formally, given a group (mathematics), group under a binary operation  ...
s of the friendly giant. The remaining six sporadic groups do not divide the order of the friendly giant, which are termed the ''
pariahs'' (
''Ly'',
''O'N'',
''Ru'',
''J''4,
''J''3, and
''J''1).
6 is the smallest integer which is not an exponent of 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 composite number. For example, 5 is prime ...
, making it the smallest integer greater than 1 for which there does not exist a
finite field
In mathematics, a finite field or Galois field (so-named in honor of Évariste Galois) is a field (mathematics), field that contains a finite number of Element (mathematics), elements. As with any field, a finite field is a Set (mathematics), s ...
of that size.
List of basic calculations
Greek and Latin word parts
'
' is classical
Greek for "six".
Thus:
*"
Hexadecimal
Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...
" combines ' with the Latinate ' to name a
number base of 16
*A
hexagon is a
regular polygon with six sides
**' is a French nickname for the continental part of
Metropolitan France for its resemblance to a
regular hexagon
*A
hexahedron is a
polyhedron with six faces, with a
cube being a special case
*
Hexameter is a poetic form consisting of six feet per line
*A "hex nut" is a
nut with six sides, and a hex
bolt has a six-sided head
*The prefix "" also occurs in the
systematic name of many
chemical compounds, such as
hexane which has 6 carbon atoms ().
The prefix ''sex-''
''Sex-'' is a
Latin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
prefix meaning "six".
Thus:
*''Senary'' is the ordinal adjective meaning "sixth"
*People with
sexdactyly have six fingers on each hand
*The measuring instrument called a
sextant got its name because its shape forms one-sixth of a whole
circle
A circle is a shape consisting of all point (geometry), points in a plane (mathematics), plane that are at a given distance from a given point, the Centre (geometry), centre. The distance between any point of the circle and the centre is cal ...
*A group of six musicians is called a
sextet
*Six babies delivered in one birth are
sextuplets
*
Sexy prime pairs – Prime pairs differing by six are ''sexy'', because sex is the Latin word for six.
The
SI prefix for 1000
6 is
exa- (E), and for its reciprocal
atto- (a).
Evolution of the Hindu-Arabic digit

The evolution of the modern digit 6 appears to be more simple when compared with the other digits. The modern 6 can be traced back to the
Brahmi numerals of
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
, which are first known from the
Edicts of Ashoka . It was written in one stroke like a cursive lowercase e rotated 90 degrees clockwise. Gradually, the upper part of the stroke (above the central squiggle) became more curved, while the lower part of the stroke (below the central squiggle) became straighter. The Arabs dropped the part of the stroke below the squiggle. From there, the European evolution to our modern 6 was very straightforward, aside from a flirtation with a glyph that looked more like an uppercase G.
On the
seven-segment displays of calculators and watches, 6 is usually written with six segments. Some historical calculator models use just five segments for the 6, by omitting the top horizontal bar. This glyph variant has not caught on; for calculators that can display results in hexadecimal, a 6 that looks like a "b" is not practical.
Just as in most modern
typeface
A typeface (or font family) is a design of Letter (alphabet), letters, Numerical digit, numbers and other symbols, to be used in printing or for electronic display. Most typefaces include variations in size (e.g., 24 point), weight (e.g., light, ...
s, in typefaces with
text figures the character for the digit 6 usually has an
ascender, as, for example, in

.
This digit resembles an inverted ''9''. To disambiguate the two on objects and documents that can be inverted, the 6 has often been underlined, both in handwriting and on printed labels.
Chemistry

*The sixfold
symmetry of
snowflakes arises from the
hexagonal
crystal structure of
ordinary ice.
Anthropology
*A
coffin is traditionally buried six feet under the ground; thus, the phrase "six feet under" means that a person (or thing, or concept) is dead.
*Six is a lucky
number in Chinese culture.
*"Six" is used as an informal slang term for the British
Secret Intelligence Service, MI6.
See also
*
Six degrees (disambiguation).
References
*
*''A Property of the Number Six'', Chapter 6, P Cameron, JH v. Lint, ''Designs, Graphs, Codes and their Links''
*Wells, D. ''The Penguin Dictionary of Curious and Interesting Numbers'' London: Penguin Group. (1987): 67 - 69
External links
The Number 6The Positive Integer 6
{{DEFAULTSORT:6 (Number)
Integers
6 (number)