21621555631564 has 24 divisors (see below), whose sum is σ = 44297821296288. Its totient is φ = 9040371692160.

The previous prime is 21621555631541. The next prime is 21621555631567. The reversal of 21621555631564 is 46513655512612.

It is not an unprimeable number, because it can be changed into a prime (21621555631567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9417052699 + ... + 9417054994.

It is an arithmetic number, because the mean of its divisors is an integer number (1845742554012).

Almost surely, 2^{21621555631564} is an apocalyptic number.

It is an amenable number.

21621555631564 is an abundant number, since it is smaller than the sum of its proper divisors (22676265664724).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21621555631564 is a wasteful number, since it uses less digits than its factorization.

21621555631564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18834107745 (or 18834107743 counting only the distinct ones).

The product of its digits is 6480000, while the sum is 52.

The spelling of 21621555631564 in words is "twenty-one trillion, six hundred twenty-one billion, five hundred fifty-five million, six hundred thirty-one thousand, five hundred sixty-four".