639856764 has 36 divisors (see below), whose sum is σ = 1621609080. Its totient is φ = 212732640.

The previous prime is 639856759. The next prime is 639856817. The reversal of 639856764 is 467658936.

It is a tau number, because it is divible by the number of its divisors (36).

It is a self number, because there is not a number n which added to its sum of digits gives 639856764.

It is a congruent number.

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, 8842 + ... + 36849.

Almost surely, 2^639856764 is an apocalyptic number.

It is an amenable number.

639856764 is an abundant number, since it is smaller than the sum of its proper divisors (981752316).

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

639856764 is a wasteful number, since it uses less digits than its factorization.

639856764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46090 (or 46085 counting only the distinct ones).

The product of its digits is 6531840, while the sum is 54.

The square root of 639856764 is about 25295.3901729149. The cubic root of 639856764 is about 861.7095810895.

The spelling of 639856764 in words is "six hundred thirty-nine million, eight hundred fifty-six thousand, seven hundred sixty-four".