21656215677 has 32 divisors (see below), whose sum is σ = 29721168000. Its totient is φ = 14020966400.

The previous prime is 21656215667. The next prime is 21656215681. The reversal of 21656215677 is 77651265612.

It is a cyclic number.

It is not a de Polignac number, because 21656215677 - 2⁴ = 21656215661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656215657) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10170949 + ... + 10173077.

It is an arithmetic number, because the mean of its divisors is an integer number (928786500).

Almost surely, 2^21656215677 is an apocalyptic number.

It is an amenable number.

21656215677 is a deficient number, since it is larger than the sum of its proper divisors (8064952323).

21656215677 is a wasteful number, since it uses less digits than its factorization.

21656215677 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2861.

The product of its digits is 1058400, while the sum is 48.

The spelling of 21656215677 in words is "twenty-one billion, six hundred fifty-six million, two hundred fifteen thousand, six hundred seventy-seven".