639666680 has 32 divisors (see below), whose sum is σ = 1440050400. Its totient is φ = 255724416.

The previous prime is 639666631. The next prime is 639666691. The reversal of 639666680 is 86666936.

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, 96926 + ... + 103314.

It is an arithmetic number, because the mean of its divisors is an integer number (45001575).

Almost surely, 2^639666680 is an apocalyptic number.

It is an amenable number.

639666680 is an abundant number, since it is smaller than the sum of its proper divisors (800383720).

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

639666680 is a wasteful number, since it uses less digits than its factorization.

639666680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8903 (or 8899 counting only the distinct ones).

The product of its (nonzero) digits is 1679616, while the sum is 50.

The square root of 639666680 is about 25291.6326084340. The cubic root of 639666680 is about 861.6242424971.

The spelling of 639666680 in words is "six hundred thirty-nine million, six hundred sixty-six thousand, six hundred eighty".