721898139664 has 20 divisors (see below), whose sum is σ = 1506268234156. Its totient is φ = 333183756672.

The previous prime is 721898139661. The next prime is 721898139673. The reversal of 721898139664 is 466931898127.

It can be written as a sum of positive squares in 2 ways, for example, as 177561104400 + 544337035264 = 421380^2 + 737792^2 .

It is a super-2 number, since 2×721898139664² (a number of 25 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 721898139596 and 721898139605.

It is not an unprimeable number, because it can be changed into a prime (721898139661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1735331859 + ... + 1735332274.

Almost surely, 2^721898139664 is an apocalyptic number.

It is an amenable number.

721898139664 is an abundant number, since it is smaller than the sum of its proper divisors (784370094492).

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

721898139664 is a wasteful number, since it uses less digits than its factorization.

721898139664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3470664154 (or 3470664148 counting only the distinct ones).

The product of its digits is 31352832, while the sum is 64.

The spelling of 721898139664 in words is "seven hundred twenty-one billion, eight hundred ninety-eight million, one hundred thirty-nine thousand, six hundred sixty-four".