21637621854 has 20 divisors (see below), whose sum is σ = 48484301184. Its totient is φ = 7212540564.

The previous prime is 21637621843. The next prime is 21637621891. The reversal of 21637621854 is 45812673612.

21637621854 is a `hidden beast` number, since 2 + 1 + 637 + 6 + 2 + 1 + 8 + 5 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 66782622 + ... + 66782945.

Almost surely, 2^21637621854 is an apocalyptic number.

21637621854 is an abundant number, since it is smaller than the sum of its proper divisors (26846679330).

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

21637621854 is a wasteful number, since it uses less digits than its factorization.

21637621854 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133565581 (or 133565572 counting only the distinct ones).

The product of its digits is 483840, while the sum is 45.

The spelling of 21637621854 in words is "twenty-one billion, six hundred thirty-seven million, six hundred twenty-one thousand, eight hundred fifty-four".