21638428220637 has 32 divisors (see below), whose sum is σ = 33944322360960. Its totient is φ = 13576377058560.

The previous prime is 21638428220599. The next prime is 21638428220653. The reversal of 21638428220637 is 73602282483612.

21638428220637 is a `hidden beast` number, since 2 + 1 + 6 + 3 + 8 + 428 + 2 + 206 + 3 + 7 = 666.

It is not a de Polignac number, because 21638428220637 - 2⁷ = 21638428220509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21638428220537) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8136418 + ... + 10463180.

It is an arithmetic number, because the mean of its divisors is an integer number (1060760073780).

Almost surely, 2^{21638428220637} is an apocalyptic number.

21638428220637 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21638428220637 is a deficient number, since it is larger than the sum of its proper divisors (12305894140323).

21638428220637 is a wasteful number, since it uses less digits than its factorization.

21638428220637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2347050 (or 2347044 counting only the distinct ones).

The product of its (nonzero) digits is 9289728, while the sum is 54.

The spelling of 21638428220637 in words is "twenty-one trillion, six hundred thirty-eight billion, four hundred twenty-eight million, two hundred twenty thousand, six hundred thirty-seven".