85 (eighty-five) 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
84 and preceding
86.
In mathematics
85 is:
* the product of two
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 ...
s (5 and 17), and is therefore a
semiprime of the form (5.q) where q is prime.
* specifically, the 24th
Semiprime, it being the fourth of the form (5.q).
*together with
86 and
87, forms the second cluster of three consecutive
semiprimes; the first comprising
33,
34,
35.
* with a prime
aliquot sum
In number theory, the aliquot sum of a positive integer is the sum of all proper divisors of , that is, all divisors of other than itself.
That is,
s(n)=\sum_ d \, .
It can be used to characterize the prime numbers, perfect numbers, sociabl ...
of
23 in the short
aliquot sequence
In mathematics, an aliquot sequence is a sequence of positive integers in which each term is the sum of the proper divisors of the previous term. If the sequence reaches the number 1, it ends, since the sum of the proper divisors of 1 is 0.
Def ...
(85,
23,
1,0).
* an
octahedral number
In number theory, an octahedral number is a figurate number that represents the number of spheres in an octahedron formed from close-packed spheres. The th octahedral number O_n can be obtained by the formula:.
:O_n=.
The first few octahedral ...
.
* a
centered triangular number.
* a
centered square number.
* a
decagonal number.
* the smallest number that can be expressed as a
sum of two squares, with all squares greater than 1, in two ways, 85 = 9
2 + 2
2 = 7
2 + 6
2.
* the length of the hypotenuse of four
Pythagorean triangles.
* a
Smith number in decimal.
In other fields
* The radix of the
Ascii85
Ascii85, also called Base85, is a form of binary-to-text encoding developed by Paul E. Rutter for the btoa utility. By using five ASCII characters to represent four bytes of binary data (making the encoded size larger than the original, assuming e ...
(sometimes called Base85) binary-to-text encoding
* Part of the assignation for the
Toyota AE85, commonly referred to as an "eight-five".
References
External links
85* Jorge Stolfi
The Hollywood Constant
{{DEFAULTSORT:85 (Number)
Integers