721636686660 has 24 divisors (see below), whose sum is σ = 2020582722816. Its totient is φ = 192436449760.

The previous prime is 721636686619. The next prime is 721636686713. The reversal of 721636686660 is 66686636127.

It is a self number, because there is not a number n which added to its sum of digits gives 721636686660.

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, 6013638996 + ... + 6013639115.

It is an arithmetic number, because the mean of its divisors is an integer number (84190946784).

Almost surely, 2^721636686660 is an apocalyptic number.

It is an amenable number.

721636686660 is an abundant number, since it is smaller than the sum of its proper divisors (1298946036156).

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

721636686660 is a wasteful number, since it uses less digits than its factorization.

721636686660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12027278123 (or 12027278121 counting only the distinct ones).

The product of its (nonzero) digits is 15676416, while the sum is 57.

The spelling of 721636686660 in words is "seven hundred twenty-one billion, six hundred thirty-six million, six hundred eighty-six thousand, six hundred sixty".