21638638172 has 24 divisors (see below), whose sum is σ = 38384959872. Its totient is φ = 10671922800.

The previous prime is 21638638171. The next prime is 21638638181. The reversal of 21638638172 is 27183683612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21638638171) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 157847 + ... + 261137.

It is an arithmetic number, because the mean of its divisors is an integer number (1599373328).

Almost surely, 2^21638638172 is an apocalyptic number.

It is an amenable number.

21638638172 is a deficient number, since it is larger than the sum of its proper divisors (16746321700).

21638638172 is a wasteful number, since it uses less digits than its factorization.

21638638172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104009 (or 104007 counting only the distinct ones).

The product of its digits is 580608, while the sum is 47.

The spelling of 21638638172 in words is "twenty-one billion, six hundred thirty-eight million, six hundred thirty-eight thousand, one hundred seventy-two".