639633904 has 120 divisors (see below), whose sum is σ = 1568471040. Its totient is φ = 247313664.

The previous prime is 639633893. The next prime is 639633913. The reversal of 639633904 is 409336936.

It is a super-2 number, since 2×639633904² = 818263062292562432, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 889257 + ... + 889975.

It is an arithmetic number, because the mean of its divisors is an integer number (13070592).

Almost surely, 2^639633904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639633904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (784235520).

639633904 is an abundant number, since it is smaller than the sum of its proper divisors (928837136).

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

639633904 is a wasteful number, since it uses less digits than its factorization.

639633904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 807 (or 788 counting only the distinct ones).

The product of its (nonzero) digits is 314928, while the sum is 43.

The square root of 639633904 is about 25290.9846387997. The cubic root of 639633904 is about 861.6095259375.

The spelling of 639633904 in words is "six hundred thirty-nine million, six hundred thirty-three thousand, nine hundred four".