639128908 has 24 divisors (see below), whose sum is σ = 1243181520. Its totient is φ = 285030720.

The previous prime is 639128863. The next prime is 639128929. The reversal of 639128908 is 809821936.

It is a super-2 number, since 2×639128908² = 816971522082544928, which contains 22 as substring.

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, 134703 + ... + 139366.

It is an arithmetic number, because the mean of its divisors is an integer number (51799230).

Almost surely, 2^639128908 is an apocalyptic number.

It is an amenable number.

639128908 is a deficient number, since it is larger than the sum of its proper divisors (604052612).

639128908 is a wasteful number, since it uses less digits than its factorization.

639128908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274137 (or 274135 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 46.

The square root of 639128908 is about 25280.9989517819. The cubic root of 639128908 is about 861.3827170712.

The spelling of 639128908 in words is "six hundred thirty-nine million, one hundred twenty-eight thousand, nine hundred eight".