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
Nth root real. Finally, if "x" is not real, then none of its "n"th roots is real. Roots are usually written using the radical symbol or "radix" with formula_2 denoting the principal square root of formula_3, formula_4 denoting the principal cube root, formula_5 denoting the principal fourth root, and so on. In the expression formula_6, "n" is called the "index", formula_7 is the "radical sign" or "radix", and formula_3 is called the "radicand". Since the radical symbol denotes a function, it is defined to return only one result for a given argument formula_3, which is called the principal "n"th root of formula_3.