639125866 has 4 divisors (see below), whose sum is σ = 958688802. Its totient is φ = 319562932.

The previous prime is 639125843. The next prime is 639125951. The reversal of 639125866 is 668521936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 598536225 + 40589641 = 24465^2 + 6371^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159781465 + ... + 159781468.

Almost surely, 2^639125866 is an apocalyptic number.

639125866 is a deficient number, since it is larger than the sum of its proper divisors (319562936).

639125866 is a wasteful number, since it uses less digits than its factorization.

639125866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319562935.

The product of its digits is 466560, while the sum is 46.

The square root of 639125866 is about 25280.9387879485. The cubic root of 639125866 is about 861.3813504557.

The spelling of 639125866 in words is "six hundred thirty-nine million, one hundred twenty-five thousand, eight hundred sixty-six".