27

27 (twenty-seven) is the natural number following 26 and preceding 28. Twenty-seven is the smallest positive integer requiring four syllables to name in English, though it can be unambiguously defined in just two: "three cubed."

Twenty-seven is a perfect cube, being 3³ = 3 × 3 × 3. 27 is therefore the second smallest cube of a prime number. 27 is 3↑↑2 (using Knuth's up-arrow notation). There are exactly 27 straight lines on a cubic surface. 27 is also a decagonal number.27 has an aliquot sum of 13 and is the first composite member of the 13-aliquot tree with the aliquot sequence (27,13,1,0)In base 10, it is the first composite number not evenly divisible by any of its digits. It is the radix (base) of the septemvigesimal positional numeral system.In a prime reciprocal magic square of the multiples of 1/7, the magic constant is 27.It is the twenty-eighth (and twenty-ninth) digit in --. (3.141592653589793238462643383279...).If you start counting with 0 it is considered one of few Self-Locating strings in pi.In base 10, it is a Smith number and a Harshad number.The unique simple formally real Jordan algebra, the exceptional Jordan algebra of self-adjoint 3 by 3 matrices of quaternions, is 27-dimensional.In the Collatz conjecture (aka the "3n + 1 conjecture") a starting value of 27 requires 112 steps to reach 1, many more than any lower number.

There are a total of 27 books in the New Testament