21505044564 has 24 divisors (see below), whose sum is σ = 55753819520. Its totient is φ = 7168348152.

The previous prime is 21505044563. The next prime is 21505044571. The reversal of 21505044564 is 46544050512.

21505044564 is a `hidden beast` number, since 2 + 1 + 5 + 0 + 50 + 44 + 564 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505044563) 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, 99560284 + ... + 99560499.

Almost surely, 2^21505044564 is an apocalyptic number.

It is an amenable number.

21505044564 is an abundant number, since it is smaller than the sum of its proper divisors (34248774956).

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

21505044564 is a wasteful number, since it uses less digits than its factorization.

21505044564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199120796 (or 199120788 counting only the distinct ones).

The product of its (nonzero) digits is 96000, while the sum is 36.

The spelling of 21505044564 in words is "twenty-one billion, five hundred five million, forty-four thousand, five hundred sixty-four".