21163904 has 16 divisors (see below), whose sum is σ = 42162720. Its totient is φ = 10581888.

The previous prime is 21163867. The next prime is 21163927. The reversal of 21163904 is 40936112.

It is a tau number, because it is divible by the number of its divisors (16).

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 82544 + ... + 82799.

It is an arithmetic number, because the mean of its divisors is an integer number (2635170).

Almost surely, 2^21163904 is an apocalyptic number.

It is an amenable number.

21163904 is a deficient number, since it is larger than the sum of its proper divisors (20998816).

21163904 is an equidigital number, since it uses as much as digits as its factorization.

21163904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165357 (or 165345 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21163904 is about 4600.4243282549. The cubic root of 21163904 is about 276.6083340190.

The spelling of 21163904 in words is "twenty-one million, one hundred sixty-three thousand, nine hundred four".