85 (eighty-five) is the natural number following 84 and preceding 86.
In mathematics 85 is: the product of two prime numbers (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 of 23 in the short aliquot sequence (85,23,1,0). an octahedral number. 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 = 92 + 22 = 72 + 62.. The two smaller numbers on this list, 50 and 65, have 1 as one of the squares in their representations as sums of two squares. the length of the hypotenuse of four Pythagorean triangles. a Smith number in decimal.
In other fields
The radix of the Ascii85 (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.