21120566721 has 16 divisors (see below), whose sum is σ = 28294526400. Its totient is φ = 14013540288.

The previous prime is 21120566711. The next prime is 21120566759. The reversal of 21120566721 is 12766502112.

It is not a de Polignac number, because 21120566721 - 2⁵ = 21120566689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21120566711) 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, 2707695 + ... + 2715483.

It is an arithmetic number, because the mean of its divisors is an integer number (1768407900).

Almost surely, 2^21120566721 is an apocalyptic number.

It is an amenable number.

21120566721 is a deficient number, since it is larger than the sum of its proper divisors (7173959679).

21120566721 is a wasteful number, since it uses less digits than its factorization.

21120566721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11968.

The product of its (nonzero) digits is 10080, while the sum is 33.

The spelling of 21120566721 in words is "twenty-one billion, one hundred twenty million, five hundred sixty-six thousand, seven hundred twenty-one".