21544621056 has 924 divisors, whose sum is σ = 81619294080. Its totient is φ = 5643509760.

The previous prime is 21544621039. The next prime is 21544621061. The reversal of 21544621056 is 65012644512.

21544621056 is a `hidden beast` number, since 2 + 1 + 544 + 6 + 2 + 105 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21544621056.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 694987761 + ... + 694987791.

Almost surely, 2^21544621056 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21544621056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40809647040).

21544621056 is an abundant number, since it is smaller than the sum of its proper divisors (60074673024).

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

21544621056 is an equidigital number, since it uses as much as digits as its factorization.

21544621056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102 (or 62 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The spelling of 21544621056 in words is "twenty-one billion, five hundred forty-four million, six hundred twenty-one thousand, fifty-six".