64 (number) it is possible to find sequences of 64 consecutive integers such that each inner member shares a factor with either the first or the last member, 64 is an Erdős–Woods number. In base 10, no integer added up to its own digits yields 64, hence it is a self number. 64 is a superperfect number—a number such that σ(σ("n")) = 2"n". 64 is the index of Graham's number in the rapidly growing sequence 3↑↑↑↑3, 3 ↑ 3,… Sixty-four is: 64 (number) 64 (sixty-four) is the natural number following 63 and preceding 65. Sixty-four is the square of 8, the cube
Square-free integer (that is a integer such that is divisible by the square of every prime factor) and a square-free integer, which are coprime. The square-free factor, called the "square-free part" of the number, is the largest square-free divisor of that is coprime with . The square-free part of an integer may be smaller than the largest square-free divisor. Any arbitrary positive integer can be represented in a unique way as the product of a square and a square-free integer : In this factorization, is the largest divisor of " such that is a divisor of . In summary, there are three