21566552868 has 54 divisors (see below), whose sum is σ = 63415940406. Its totient is φ = 6161871744.

The previous prime is 21566552857. The next prime is 21566552893. The reversal of 21566552868 is 86825566512.

It is a happy number.

21566552868 is a `hidden beast` number, since 2 + 1 + 5 + 6 + 6 + 552 + 86 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 12707601984 + 8858950884 = 112728^2 + 94122^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 6111205 + ... + 6114732.

Almost surely, 2^21566552868 is an apocalyptic number.

21566552868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21566552868 is an abundant number, since it is smaller than the sum of its proper divisors (41849387538).

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

21566552868 is a wasteful number, since it uses less digits than its factorization.

21566552868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12225961 (or 12225949 counting only the distinct ones).

The product of its digits is 6912000, while the sum is 54.

The spelling of 21566552868 in words is "twenty-one billion, five hundred sixty-six million, five hundred fifty-two thousand, eight hundred sixty-eight".