639605621668 has 96 divisors (see below), whose sum is σ = 1291468147200. Its totient is φ = 274717287936.

The previous prime is 639605621659. The next prime is 639605621713. The reversal of 639605621668 is 866126506936.

It is a super-2 number, since 2×639605621668² (a number of 24 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15355446 + ... + 15397042.

It is an arithmetic number, because the mean of its divisors is an integer number (13452793200).

Almost surely, 2^639605621668 is an apocalyptic number.

It is an amenable number.

639605621668 is an abundant number, since it is smaller than the sum of its proper divisors (651862525532).

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

639605621668 is a wasteful number, since it uses less digits than its factorization.

639605621668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41909 (or 41907 counting only the distinct ones).

The product of its (nonzero) digits is 16796160, while the sum is 58.

The spelling of 639605621668 in words is "six hundred thirty-nine billion, six hundred five million, six hundred twenty-one thousand, six hundred sixty-eight".