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
Integer triangle double triangular number ( + 1) and for "c" odd it is the square . It also means that the number of integer triangles with greatest side "c" exceeds the number of integer triangles with greatest side "c"−2 by "c". The sequence of the number of non-congruent integer triangles with largest side "c", starting at "c" = 1, is: The number of integer triangles (up to congruence) with given largest side "c" and integer triple ("a", "b", "c") that lie on or within a semicircle of diameter "c" is the number of integer triples such that "a" + "b" >