721624921 has 6 divisors (see below), whose sum is σ = 761604522. Its totient is φ = 683644320.

The previous prime is 721624873. The next prime is 721624973. The reversal of 721624921 is 129426127.

721624921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 614792025 + 106832896 = 24795^2 + 10336^2 .

It is not a de Polignac number, because 721624921 - 2²¹ = 719527769 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721624021) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 999120 + ... + 999841.

It is an arithmetic number, because the mean of its divisors is an integer number (126934087).

Almost surely, 2^721624921 is an apocalyptic number.

It is an amenable number.

721624921 is a deficient number, since it is larger than the sum of its proper divisors (39979601).

721624921 is a wasteful number, since it uses less digits than its factorization.

721624921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1998999 (or 1998980 counting only the distinct ones).

The product of its digits is 12096, while the sum is 34.

The square root of 721624921 is about 26863.0772809073. The cubic root of 721624921 is about 896.9546953766.

The spelling of 721624921 in words is "seven hundred twenty-one million, six hundred twenty-four thousand, nine hundred twenty-one".