639634856 has 16 divisors (see below), whose sum is σ = 1370646240. Its totient is φ = 274129200.

The previous prime is 639634819. The next prime is 639634859. The reversal of 639634856 is 658436936.

It is not an unprimeable number, because it can be changed into a prime (639634859) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5710970 + ... + 5711081.

It is an arithmetic number, because the mean of its divisors is an integer number (85665390).

Almost surely, 2^639634856 is an apocalyptic number.

It is an amenable number.

639634856 is an abundant number, since it is smaller than the sum of its proper divisors (731011384).

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

639634856 is a wasteful number, since it uses less digits than its factorization.

639634856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11422064 (or 11422060 counting only the distinct ones).

The product of its digits is 2799360, while the sum is 50.

The square root of 639634856 is about 25291.0034597285. The cubic root of 639634856 is about 861.6099533965.

The spelling of 639634856 in words is "six hundred thirty-nine million, six hundred thirty-four thousand, eight hundred fifty-six".