21137904 has 60 divisors (see below), whose sum is σ = 59556952. Its totient is φ = 6998400.

The previous prime is 21137891. The next prime is 21137911. The reversal of 21137904 is 40973112.

It is a super-3 number, since 3×21137904³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25659 + ... + 26469.

Almost surely, 2^21137904 is an apocalyptic number.

21137904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21137904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29778476).

21137904 is an abundant number, since it is smaller than the sum of its proper divisors (38419048).

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

21137904 is a wasteful number, since it uses less digits than its factorization.

21137904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1006 (or 997 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21137904 is about 4597.5976335473. The cubic root of 21137904 is about 276.4950158624.

The spelling of 21137904 in words is "twenty-one million, one hundred thirty-seven thousand, nine hundred four".