721756666920 has 64 divisors (see below), whose sum is σ = 2165326914240. Its totient is φ = 192463385600.

The previous prime is 721756666901. The next prime is 721756666921. The reversal of 721756666920 is 29666657127.

It is a Smith number, since the sum of its digits (57) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (721756666921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7604155 + ... + 7698485.

It is an arithmetic number, because the mean of its divisors is an integer number (33833233035).

Almost surely, 2^721756666920 is an apocalyptic number.

It is an amenable number.

721756666920 is an abundant number, since it is smaller than the sum of its proper divisors (1443570247320).

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

721756666920 is a wasteful number, since it uses less digits than its factorization.

721756666920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158106 (or 158102 counting only the distinct ones).

The product of its (nonzero) digits is 11430720, while the sum is 57.

The spelling of 721756666920 in words is "seven hundred twenty-one billion, seven hundred fifty-six million, six hundred sixty-six thousand, nine hundred twenty".