21138204 has 12 divisors (see below), whose sum is σ = 49322504. Its totient is φ = 7046064.

The previous prime is 21138179. The next prime is 21138209. The reversal of 21138204 is 40283112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 880747 + ... + 880770.

Almost surely, 2^21138204 is an apocalyptic number.

It is an amenable number.

21138204 is an abundant number, since it is smaller than the sum of its proper divisors (28184300).

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

21138204 is a wasteful number, since it uses less digits than its factorization.

21138204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1761524 (or 1761522 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21138204 is about 4597.6302591661. The cubic root of 21138204 is about 276.4963239093.

The spelling of 21138204 in words is "twenty-one million, one hundred thirty-eight thousand, two hundred four".