21638120 has 32 divisors (see below), whose sum is σ = 55641600. Its totient is φ = 7418688.

The previous prime is 21638117. The next prime is 21638129. The reversal of 21638120 is 2183612.

It is not an unprimeable number, because it can be changed into a prime (21638129) 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, 38360 + ... + 38919.

It is an arithmetic number, because the mean of its divisors is an integer number (1738800).

Almost surely, 2^21638120 is an apocalyptic number.

21638120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21638120 is an abundant number, since it is smaller than the sum of its proper divisors (34003480).

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

21638120 is a wasteful number, since it uses less digits than its factorization.

21638120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77297 (or 77293 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21638120 is about 4651.6792666735. The cubic root of 21638120 is about 278.6590646288.

The spelling of 21638120 in words is "twenty-one million, six hundred thirty-eight thousand, one hundred twenty".