21661612 has 24 divisors (see below), whose sum is σ = 44382240. Its totient is φ = 9056640.

The previous prime is 21661609. The next prime is 21661639. The reversal of 21661612 is 21616612.

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, 8287 + ... + 10582.

It is an arithmetic number, because the mean of its divisors is an integer number (1849260).

Almost surely, 2^21661612 is an apocalyptic number.

It is an amenable number.

21661612 is an abundant number, since it is smaller than the sum of its proper divisors (22720628).

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

21661612 is a wasteful number, since it uses less digits than its factorization.

21661612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18921 (or 18919 counting only the distinct ones).

The product of its digits is 864, while the sum is 25.

The square root of 21661612 is about 4654.2036912881. The cubic root of 21661612 is about 278.7598726956.

The spelling of 21661612 in words is "twenty-one million, six hundred sixty-one thousand, six hundred twelve".