21395904 has 56 divisors (see below), whose sum is σ = 57838848. Its totient is φ = 6977280.

The previous prime is 21395903. The next prime is 21395929. The reversal of 21395904 is 40959312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21395903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7839 + ... + 10209.

Almost surely, 2^21395904 is an apocalyptic number.

21395904 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 21395904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28919424).

21395904 is an abundant number, since it is smaller than the sum of its proper divisors (36442944).

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

21395904 is a wasteful number, since it uses less digits than its factorization.

21395904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2433 (or 2423 counting only the distinct ones).

The product of its (nonzero) digits is 9720, while the sum is 33.

The square root of 21395904 is about 4625.5706674961. The cubic root of 21395904 is about 277.6153955589.

The spelling of 21395904 in words is "twenty-one million, three hundred ninety-five thousand, nine hundred four".