21815212 has 6 divisors (see below), whose sum is σ = 38176628. Its totient is φ = 10907604.

The previous prime is 21815207. The next prime is 21815243. The reversal of 21815212 is 21251812.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2726898 + ... + 2726905.

Almost surely, 2^21815212 is an apocalyptic number.

It is an amenable number.

21815212 is a deficient number, since it is larger than the sum of its proper divisors (16361416).

21815212 is a wasteful number, since it uses less digits than its factorization.

21815212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5453807 (or 5453805 counting only the distinct ones).

The product of its digits is 320, while the sum is 22.

The square root of 21815212 is about 4670.6757541067. The cubic root of 21815212 is about 279.4172061781.

The spelling of 21815212 in words is "twenty-one million, eight hundred fifteen thousand, two hundred twelve".