721990656 has 66 divisors (see below), whose sum is σ = 2084758962. Its totient is φ = 240660480.

The previous prime is 721990639. The next prime is 721990669. The reversal of 721990656 is 656099127.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 676832256 + 45158400 = 26016^2 + 6720^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 29955 + ... + 48386.

It is an arithmetic number, because the mean of its divisors is an integer number (31587257).

Almost surely, 2^721990656 is an apocalyptic number.

It is an amenable number.

721990656 is an abundant number, since it is smaller than the sum of its proper divisors (1362768306).

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

721990656 is a wasteful number, since it uses less digits than its factorization.

721990656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78367 (or 78346 counting only the distinct ones).

The product of its (nonzero) digits is 204120, while the sum is 45.

The square root of 721990656 is about 26869.8838106904. The cubic root of 721990656 is about 897.1062017483.

The spelling of 721990656 in words is "seven hundred twenty-one million, nine hundred ninety thousand, six hundred fifty-six".