21561637448 has 32 divisors (see below), whose sum is σ = 43545847800. Its totient is φ = 9949713408.

The previous prime is 21561637441. The next prime is 21561637501. The reversal of 21561637448 is 84473616512.

It can be written as a sum of positive squares in 4 ways, for example, as 9347409124 + 12214228324 = 96682^2 + 110518^2 .

It is a hoax number, since the sum of its digits (47) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21561637441) 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, 678458 + ... + 709526.

Almost surely, 2^21561637448 is an apocalyptic number.

It is an amenable number.

21561637448 is an abundant number, since it is smaller than the sum of its proper divisors (21984210352).

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

21561637448 is a wasteful number, since it uses less digits than its factorization.

21561637448 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37761 (or 37757 counting only the distinct ones).

The product of its digits is 967680, while the sum is 47.

The spelling of 21561637448 in words is "twenty-one billion, five hundred sixty-one million, six hundred thirty-seven thousand, four hundred forty-eight".