21666252 has 12 divisors (see below), whose sum is σ = 50554616. Its totient is φ = 7222080.

The previous prime is 21666247. The next prime is 21666263. The reversal of 21666252 is 25266612.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 902749 + ... + 902772.

Almost surely, 2^21666252 is an apocalyptic number.

It is an amenable number.

21666252 is an abundant number, since it is smaller than the sum of its proper divisors (28888364).

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

21666252 is a wasteful number, since it uses less digits than its factorization.

21666252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1805528 (or 1805526 counting only the distinct ones).

The product of its digits is 8640, while the sum is 30.

The square root of 21666252 is about 4654.7021386980. The cubic root of 21666252 is about 278.7797750843.

The spelling of 21666252 in words is "twenty-one million, six hundred sixty-six thousand, two hundred fifty-two".