21621404631656 has 16 divisors (see below), whose sum is σ = 42673824931200. Its totient is φ = 10241717983344.

The previous prime is 21621404631653. The next prime is 21621404631667. The reversal of 21621404631656 is 65613640412612.

It is a self number, because there is not a number n which added to its sum of digits gives 21621404631656.

It is not an unprimeable number, because it can be changed into a prime (21621404631653) 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, 71123041400 + ... + 71123041703.

It is an arithmetic number, because the mean of its divisors is an integer number (2667114058200).

Almost surely, 2^{21621404631656} is an apocalyptic number.

It is an amenable number.

21621404631656 is a deficient number, since it is larger than the sum of its proper divisors (21052420299544).

21621404631656 is a wasteful number, since it uses less digits than its factorization.

21621404631656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142246083128 (or 142246083124 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 47.

The spelling of 21621404631656 in words is "twenty-one trillion, six hundred twenty-one billion, four hundred four million, six hundred thirty-one thousand, six hundred fifty-six".