21177656321 has 16 divisors (see below), whose sum is σ = 21656947200. Its totient is φ = 20704439808.

The previous prime is 21177656317. The next prime is 21177656327. The reversal of 21177656321 is 12365677112.

It is a cyclic number.

It is not a de Polignac number, because 21177656321 - 2² = 21177656317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21177656327) 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, 4684100 + ... + 4688618.

It is an arithmetic number, because the mean of its divisors is an integer number (1353559200).

Almost surely, 2^21177656321 is an apocalyptic number.

It is an amenable number.

21177656321 is a deficient number, since it is larger than the sum of its proper divisors (479290879).

21177656321 is a wasteful number, since it uses less digits than its factorization.

21177656321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5168.

The product of its digits is 105840, while the sum is 41.

The spelling of 21177656321 in words is "twenty-one billion, one hundred seventy-seven million, six hundred fifty-six thousand, three hundred twenty-one".