21615812 has 12 divisors (see below), whose sum is σ = 38055360. Its totient is φ = 10742856.

The previous prime is 21615809. The next prime is 21615851. The reversal of 21615812 is 21851612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15512 + ... + 16847.

It is an arithmetic number, because the mean of its divisors is an integer number (3171280).

Almost surely, 2^21615812 is an apocalyptic number.

It is an amenable number.

21615812 is a deficient number, since it is larger than the sum of its proper divisors (16439548).

21615812 is a wasteful number, since it uses less digits than its factorization.

21615812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32530 (or 32528 counting only the distinct ones).

The product of its digits is 960, while the sum is 26.

The square root of 21615812 is about 4649.2808045976. The cubic root of 21615812 is about 278.5632697401.

The spelling of 21615812 in words is "twenty-one million, six hundred fifteen thousand, eight hundred twelve".