56631721521 has 4 divisors (see below), whose sum is σ = 75508962032. Its totient is φ = 37754481012.

The previous prime is 56631721513. The next prime is 56631721543. The reversal of 56631721521 is 12512713665.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 56631721521 - 2³ = 56631721513 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 56631721521.

It is not an unprimeable number, because it can be changed into a prime (56631721021) 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, 9438620251 + ... + 9438620256.

It is an arithmetic number, because the mean of its divisors is an integer number (18877240508).

Almost surely, 2^56631721521 is an apocalyptic number.

It is an amenable number.

56631721521 is a deficient number, since it is larger than the sum of its proper divisors (18877240511).

56631721521 is a wasteful number, since it uses less digits than its factorization.

56631721521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18877240510.

The product of its digits is 75600, while the sum is 39.

The spelling of 56631721521 in words is "fifty-six billion, six hundred thirty-one million, seven hundred twenty-one thousand, five hundred twenty-one".