721137818643 has 24 divisors (see below), whose sum is σ = 1057004983104. Its totient is φ = 436999123440.

The previous prime is 721137818617. The next prime is 721137818683. The reversal of 721137818643 is 346818731127.

It is not a de Polignac number, because 721137818643 - 2⁶ = 721137818579 is a prime.

It is a super-2 number, since 2×721137818643² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (721137818683) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2916996 + ... + 3154542.

It is an arithmetic number, because the mean of its divisors is an integer number (44041874296).

Almost surely, 2^721137818643 is an apocalyptic number.

721137818643 is a deficient number, since it is larger than the sum of its proper divisors (335867164461).

721137818643 is a wasteful number, since it uses less digits than its factorization.

721137818643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 245935 (or 245924 counting only the distinct ones).

The product of its digits is 1354752, while the sum is 51.

The spelling of 721137818643 in words is "seven hundred twenty-one billion, one hundred thirty-seven million, eight hundred eighteen thousand, six hundred forty-three".