21131900 has 18 divisors (see below), whose sum is σ = 45856440. Its totient is φ = 8452720.

The previous prime is 21131899. The next prime is 21131951. The reversal of 21131900 is 913112.

It is a happy number.

It is a super-2 number, since 2×21131900² = 893114395220000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 105560 + ... + 105759.

It is an arithmetic number, because the mean of its divisors is an integer number (2547580).

Almost surely, 2^21131900 is an apocalyptic number.

21131900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21131900 is an abundant number, since it is smaller than the sum of its proper divisors (24724540).

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

21131900 is a wasteful number, since it uses less digits than its factorization.

21131900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211333 (or 211326 counting only the distinct ones).

The product of its (nonzero) digits is 54, while the sum is 17.

The square root of 21131900 is about 4596.9446374739. The cubic root of 21131900 is about 276.4688348800.

The spelling of 21131900 in words is "twenty-one million, one hundred thirty-one thousand, nine hundred".