21665252 has 24 divisors (see below), whose sum is σ = 44217600. Its totient is φ = 9284520.

The previous prime is 21665251. The next prime is 21665279. The reversal of 21665252 is 25256612.

It is not an unprimeable number, because it can be changed into a prime (21665251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6524 + ... + 9267.

It is an arithmetic number, because the mean of its divisors is an integer number (1842400).

Almost surely, 2^21665252 is an apocalyptic number.

It is an amenable number.

21665252 is an abundant number, since it is smaller than the sum of its proper divisors (22552348).

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

21665252 is a wasteful number, since it uses less digits than its factorization.

21665252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15816 (or 15800 counting only the distinct ones).

The product of its digits is 7200, while the sum is 29.

The square root of 21665252 is about 4654.5947191995. The cubic root of 21665252 is about 278.7754860166.

The spelling of 21665252 in words is "twenty-one million, six hundred sixty-five thousand, two hundred fifty-two".