21660204 has 24 divisors (see below), whose sum is σ = 52738560. Its totient is φ = 6906064.

The previous prime is 21660173. The next prime is 21660211. The reversal of 21660204 is 40206612.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38964 + ... + 39515.

It is an arithmetic number, because the mean of its divisors is an integer number (2197440).

Almost surely, 2^21660204 is an apocalyptic number.

It is an amenable number.

21660204 is an abundant number, since it is smaller than the sum of its proper divisors (31078356).

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

21660204 is a wasteful number, since it uses less digits than its factorization.

21660204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78509 (or 78507 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 21660204 is about 4654.0524277236. The cubic root of 21660204 is about 278.7538327880.

Adding to 21660204 its reverse (40206612), we get a palindrome (61866816).

The spelling of 21660204 in words is "twenty-one million, six hundred sixty thousand, two hundred four".