21243204 has 36 divisors (see below), whose sum is σ = 54950896. Its totient is φ = 6915888.

The previous prime is 21243193. The next prime is 21243227. The reversal of 21243204 is 40234212.

Added to its reverse (40234212) it gives a triangular number (61477416 = T₁₁₀₈₈).

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5314 + ... + 8409.

Almost surely, 2^21243204 is an apocalyptic number.

It is an amenable number.

21243204 is an abundant number, since it is smaller than the sum of its proper divisors (33707692).

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

21243204 is a wasteful number, since it uses less digits than its factorization.

21243204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13776 (or 13771 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21243204 is about 4609.0350400057. The cubic root of 21243204 is about 276.9533822247.

Adding to 21243204 its reverse (40234212), we get a palindrome (61477416).

The spelling of 21243204 in words is "twenty-one million, two hundred forty-three thousand, two hundred four".