21656611201 has 16 divisors (see below), whose sum is σ = 22488067840. Its totient is φ = 20845693440.

The previous prime is 21656611187. The next prime is 21656611231. The reversal of 21656611201 is 10211665612.

It is a cyclic number.

It is not a de Polignac number, because 21656611201 - 2¹¹ = 21656609153 is a prime.

It is a super-2 number, since 2×21656611201² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21656611231) 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, 492331 + ... + 534511.

It is an arithmetic number, because the mean of its divisors is an integer number (1405504240).

Almost surely, 2^21656611201 is an apocalyptic number.

It is an amenable number.

21656611201 is a deficient number, since it is larger than the sum of its proper divisors (831456639).

21656611201 is an equidigital number, since it uses as much as digits as its factorization.

21656611201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42424.

The product of its (nonzero) digits is 4320, while the sum is 31.

The spelling of 21656611201 in words is "twenty-one billion, six hundred fifty-six million, six hundred eleven thousand, two hundred one".