64721664 has 108 divisors (see below), whose sum is σ = 213320016. Its totient is φ = 18487296.

The previous prime is 64721653. The next prime is 64721681. The reversal of 64721664 is 46612746.

64721664 is a `hidden beast` number, since 647 + 2 + 1 + 6 + 6 + 4 = 666.

It is a super-3 number, since 3×64721664³ (a number of 24 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14122 + ... + 18134.

Almost surely, 2^64721664 is an apocalyptic number.

64721664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 64721664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (106660008).

64721664 is an abundant number, since it is smaller than the sum of its proper divisors (148598352).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

64721664 is a wasteful number, since it uses less digits than its factorization.

64721664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4042 (or 4025 counting only the distinct ones).

The product of its digits is 48384, while the sum is 36.

The square root of 64721664 is about 8044.9775636729. The cubic root of 64721664 is about 401.4978507732.

The spelling of 64721664 in words is "sixty-four million, seven hundred twenty-one thousand, six hundred sixty-four".