639217668 has 12 divisors (see below), whose sum is σ = 1491507920. Its totient is φ = 213072552.

The previous prime is 639217643. The next prime is 639217673. The reversal of 639217668 is 866712936.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26634058 + ... + 26634081.

Almost surely, 2^639217668 is an apocalyptic number.

It is an amenable number.

639217668 is an abundant number, since it is smaller than the sum of its proper divisors (852290252).

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

639217668 is a wasteful number, since it uses less digits than its factorization.

639217668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53268146 (or 53268144 counting only the distinct ones).

The product of its digits is 653184, while the sum is 48.

The square root of 639217668 is about 25282.7543594443. The cubic root of 639217668 is about 861.4225905041.

The spelling of 639217668 in words is "six hundred thirty-nine million, two hundred seventeen thousand, six hundred sixty-eight".