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
The Simple Solution to Rubik's Cube season working out a solution, which he published as a 32-page pamphlet for the university bookstore. It reached the hands of a publisher at Bantam who persuaded Nourse to expand the guide into a 64-page book. The book was published June 1981. It became the best-selling book of 1981, selling 6,680,000 copies that year. It was the fastest-selling title in the 36-year history of Bantam Books. In November 1981 Nourse published a sequel, "The Simple Solutions to Cubic Puzzles", as an aid to the numerous puzzles that were spawned by the Cube-craze. Many later solutions to Rubik's Cube published on