21315904 has 28 divisors (see below), whose sum is σ = 42903648. Its totient is φ = 10505600.

The previous prime is 21315893. The next prime is 21315919. The reversal of 21315904 is 40951312.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2199 + ... + 6889.

Almost surely, 2^21315904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21451824).

21315904 is an abundant number, since it is smaller than the sum of its proper divisors (21587744).

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

21315904 is an equidigital number, since it uses as much as digits as its factorization.

21315904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4774 (or 4764 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21315904 is about 4616.9149873048. The cubic root of 21315904 is about 277.2689590067.

The spelling of 21315904 in words is "twenty-one million, three hundred fifteen thousand, nine hundred four".