639696256 has 64 divisors (see below), whose sum is σ = 1377918000. Its totient is φ = 294782976.

The previous prime is 639696241. The next prime is 639696269. The reversal of 639696256 is 652696936.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×639696256² = 818422599880835072, 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 7 ways as a sum of consecutive naturals, for example, 86430 + ... + 93538.

Almost surely, 2^639696256 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 639696256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (688959000).

639696256 is an abundant number, since it is smaller than the sum of its proper divisors (738221744).

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

639696256 is a wasteful number, since it uses less digits than its factorization.

639696256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7179 (or 7167 counting only the distinct ones).

The product of its digits is 3149280, while the sum is 52.

The square root of 639696256 is about 25292.2173009802. The cubic root of 639696256 is about 861.6375218121.

It can be divided in two parts, 63969 and 6256, that added together give a square (70225 = 265²).

The spelling of 639696256 in words is "six hundred thirty-nine million, six hundred ninety-six thousand, two hundred fifty-six".