20999904 has 24 divisors (see below), whose sum is σ = 55125000. Its totient is φ = 6999936.

The previous prime is 20999899. The next prime is 20999917. The reversal of 20999904 is 40999902.

It is a tau number, because it is divible by the number of its divisors (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109279 + ... + 109470.

It is an arithmetic number, because the mean of its divisors is an integer number (2296875).

Almost surely, 2^20999904 is an apocalyptic number.

20999904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

20999904 is an abundant number, since it is smaller than the sum of its proper divisors (34125096).

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

20999904 is a wasteful number, since it uses less digits than its factorization.

20999904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218762 (or 218754 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 42.

The square root of 20999904 is about 4582.5652204851. The cubic root of 20999904 is about 275.8919972300.

The spelling of 20999904 in words is "twenty million, nine hundred ninety-nine thousand, nine hundred four".