21656025636431 has 4 divisors (see below), whose sum is σ = 21750593434200. Its totient is φ = 21561457838664.

The previous prime is 21656025636359. The next prime is 21656025636461. The reversal of 21656025636431 is 13463652065612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21656025636431 - 2⁴² = 17257979125327 is a prime.

It is a super-2 number, since 2×21656025636431² (a number of 27 digits) contains 22 as substring.

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 21656025636431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656025636461) 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, 47283898541 + ... + 47283898998.

It is an arithmetic number, because the mean of its divisors is an integer number (5437648358550).

Almost surely, 2^{21656025636431} is an apocalyptic number.

21656025636431 is a deficient number, since it is larger than the sum of its proper divisors (94567797769).

21656025636431 is an equidigital number, since it uses as much as digits as its factorization.

21656025636431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94567797768.

The product of its (nonzero) digits is 4665600, while the sum is 50.

The spelling of 21656025636431 in words is "twenty-one trillion, six hundred fifty-six billion, twenty-five million, six hundred thirty-six thousand, four hundred thirty-one".