64 (number) 64 (number) 64 (sixty-four) is the natural number following 63 and preceding 65. Sixty-four is the square of 8, the cube of 4, and the sixth power of 2. It is the smallest number with exactly seven divisors. It is the lowest positive power of two that is adjacent to neither a Mersenne prime nor a Fermat prime. 64 is the sum of Euler's totient function for the first fourteen integers. It is also a dodecagonal number and a centered triangular number. 64 is also the first whole number that is both a perfect square and a perfect cube. Since
Cube root can be done with a compass-and-straightedge construction. Newton's method is an iterative method that can be used to calculate the cube root. For real floating-point numbers this method reduces to the following iterative algorithm to produce successively better approximations of the cube root of "a": The method is simply averaging three factors chosen such that at each iteration. Halley's method improves upon this with an algorithm that converges more quickly with each step, albeit consuming more multiplication operations: With either method a poor initial approximation of "x" can give very poor algorithm performance, and coming up with a good initial