64 (sixty-four) is the natural number following 63 and preceding 65.

Mathematics

Sixty-four is the square of 8, the cube of 4, and the sixth power of 2. It is the seventeenth interprime, since it lies midway between the eighteenth and nineteenth prime numbers (61, 67). The aliquot sum of a power of two (2n) is always one less than the power of two itself, therefore the aliquot sum of 64 is 63, within an aliquot sequence of two composite members (64, 63, 41, 1, 0) that are rooted in the aliquot tree of the thirteenth prime, 41. 64 is: Since it is possible to find sequences of 65 consecutive integers (intervals of length 64) such that each inner member shares a factor with either the first or the last member, 64 is the seventh Erdős–Woods number. In decimal, no integer added to the sum of its own digits yields 64; hence, 64 is the tenth self number. In four dimensions, there are 64 uniform polychora aside from two infinite families of duoprisms and antiprismatic prisms, and 64 Bravais lattices.

In other fields

Science

64 is the atomic number of gadolinium, a lanthanide. 64 is the number of codons in the RNA codon table of the genetic code. 64 is the size in bits of certain data types in some computer programming languages, where a 64-bit integer can represent values up to 264 = 18,446,744,073,709,551,616.

Gaming

64 is the number of squares in a regular eight by eight chessboard. 64 is the maximum item stack size in Minecraft, where the number is called a 'stack'. The 1996 Nintendo console is also called the Nintendo 64.

I Ching

The number of hexagrams in the I Ching (that is also the maximum number of strokes in any Chinese character).

Media

Song When I'm Sixty-Four by The Beatles