21855904 has 24 divisors (see below), whose sum is σ = 49176288. Its totient is φ = 9366720.

The previous prime is 21855887. The next prime is 21855907. The reversal of 21855904 is 40955812.

It is a self number, because there is not a number n which added to its sum of digits gives 21855904.

It is not an unprimeable number, because it can be changed into a prime (21855907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48562 + ... + 49009.

It is an arithmetic number, because the mean of its divisors is an integer number (2049012).

Almost surely, 2^21855904 is an apocalyptic number.

It is an amenable number.

21855904 is an abundant number, since it is smaller than the sum of its proper divisors (27320384).

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

21855904 is an equidigital number, since it uses as much as digits as its factorization.

21855904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97588 (or 97580 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 21855904 is about 4675.0298394770. The cubic root of 21855904 is about 279.5908309365.

The spelling of 21855904 in words is "twenty-one million, eight hundred fifty-five thousand, nine hundred four".