721137818644 has 24 divisors (see below), whose sum is σ = 1292830660800. Its totient is φ = 351758435520.

The previous prime is 721137818617. The next prime is 721137818683. The reversal of 721137818644 is 446818731127.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 721137818591 and 721137818600.

It is a congruent number.

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, 3998487 + ... + 4174945.

It is an arithmetic number, because the mean of its divisors is an integer number (53867944200).

Almost surely, 2^721137818644 is an apocalyptic number.

It is an amenable number.

721137818644 is a deficient number, since it is larger than the sum of its proper divisors (571692842156).

721137818644 is a wasteful number, since it uses less digits than its factorization.

721137818644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201423 (or 201421 counting only the distinct ones).

The product of its digits is 1806336, while the sum is 52.

The spelling of 721137818644 in words is "seven hundred twenty-one billion, one hundred thirty-seven million, eight hundred eighteen thousand, six hundred forty-four".