21561152544 has 72 divisors (see below), whose sum is σ = 61330208940. Its totient is φ = 7185212928.

The previous prime is 21561152539. The next prime is 21561152563. The reversal of 21561152544 is 44525116512.

21561152544 is a `hidden beast` number, since 2 + 1 + 5 + 61 + 1 + 52 + 544 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 16378880400 + 5182272144 = 127980^2 + 71988^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a junction number, because it is equal to n+sod(n) for n = 21561152499 and 21561152508.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1570542 + ... + 1584210.

Almost surely, 2^21561152544 is an apocalyptic number.

21561152544 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21561152544 is an abundant number, since it is smaller than the sum of its proper divisors (39769056396).

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

21561152544 is a wasteful number, since it uses less digits than its factorization.

21561152544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19162 (or 19151 counting only the distinct ones).

The product of its digits is 48000, while the sum is 36.

The spelling of 21561152544 in words is "twenty-one billion, five hundred sixty-one million, one hundred fifty-two thousand, five hundred forty-four".