21204939 has 16 divisors (see below), whose sum is σ = 32617728. Its totient is φ = 12002592.

The previous prime is 21204917. The next prime is 21204947. The reversal of 21204939 is 93940212.

It is not a de Polignac number, because 21204939 - 2⁸ = 21204683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21204949) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2472 + ... + 6965.

It is an arithmetic number, because the mean of its divisors is an integer number (2038608).

Almost surely, 2^21204939 is an apocalyptic number.

21204939 is a deficient number, since it is larger than the sum of its proper divisors (11412789).

21204939 is a wasteful number, since it uses less digits than its factorization.

21204939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9554.

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21204939 is about 4604.8820831808. The cubic root of 21204939 is about 276.7869919029.

The spelling of 21204939 in words is "twenty-one million, two hundred four thousand, nine hundred thirty-nine".