21688204 has 6 divisors (see below), whose sum is σ = 37954364. Its totient is φ = 10844100.

The previous prime is 21688187. The next prime is 21688213. The reversal of 21688204 is 40288612.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2711022 + ... + 2711029.

Almost surely, 2^21688204 is an apocalyptic number.

It is an amenable number.

21688204 is a deficient number, since it is larger than the sum of its proper divisors (16266160).

21688204 is a wasteful number, since it uses less digits than its factorization.

21688204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5422055 (or 5422053 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 31.

The square root of 21688204 is about 4657.0595873362. The cubic root of 21688204 is about 278.8738954696.

The spelling of 21688204 in words is "twenty-one million, six hundred eighty-eight thousand, two hundred four".