21353904 has 240 divisors, whose sum is σ = 75557664. Its totient is φ = 5529600.

The previous prime is 21353897. The next prime is 21353923. The reversal of 21353904 is 40935312.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 350034 + ... + 350094.

Almost surely, 2^21353904 is an apocalyptic number.

21353904 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 21353904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37778832).

21353904 is an abundant number, since it is smaller than the sum of its proper divisors (54203760).

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

21353904 is a wasteful number, since it uses less digits than its factorization.

21353904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 21353904 is about 4621.0284569563. The cubic root of 21353904 is about 277.4336242513.

The spelling of 21353904 in words is "twenty-one million, three hundred fifty-three thousand, nine hundred four".