20561252664 has 16 divisors (see below), whose sum is σ = 51403131720. Its totient is φ = 6853750880.

The previous prime is 20561252627. The next prime is 20561252671. The reversal of 20561252664 is 46625216502.

It is a super-2 number, since 2×20561252664² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 428359407 + ... + 428359454.

Almost surely, 2^20561252664 is an apocalyptic number.

20561252664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

20561252664 is an abundant number, since it is smaller than the sum of its proper divisors (30841879056).

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

20561252664 is a wasteful number, since it uses less digits than its factorization.

20561252664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856718870 (or 856718866 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 39.

The spelling of 20561252664 in words is "twenty billion, five hundred sixty-one million, two hundred fifty-two thousand, six hundred sixty-four".