21518321856 has 28 divisors (see below), whose sum is σ = 56933893752. Its totient is φ = 7172773888.

The previous prime is 21518321849. The next prime is 21518321933. The reversal of 21518321856 is 65812381512.

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, 56037105 + ... + 56037488.

Almost surely, 2^21518321856 is an apocalyptic number.

It is an amenable number.

21518321856 is an abundant number, since it is smaller than the sum of its proper divisors (35415571896).

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

21518321856 is a wasteful number, since it uses less digits than its factorization.

21518321856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112074608 (or 112074598 counting only the distinct ones).

The product of its digits is 115200, while the sum is 42.

The spelling of 21518321856 in words is "twenty-one billion, five hundred eighteen million, three hundred twenty-one thousand, eight hundred fifty-six".