21644252 has 24 divisors (see below), whose sum is σ = 44212224. Its totient is φ = 9078192.

The previous prime is 21644197. The next prime is 21644257. The reversal of 21644252 is 25244612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644257) 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, 6908 + ... + 9539.

It is an arithmetic number, because the mean of its divisors is an integer number (1842176).

Almost surely, 2^21644252 is an apocalyptic number.

It is an amenable number.

21644252 is an abundant number, since it is smaller than the sum of its proper divisors (22567972).

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

21644252 is a wasteful number, since it uses less digits than its factorization.

21644252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16505 (or 16503 counting only the distinct ones).

The product of its digits is 3840, while the sum is 26.

The square root of 21644252 is about 4652.3383367937. The cubic root of 21644252 is about 278.6853850916.

Adding to 21644252 its reverse (25244612), we get a palindrome (46888864).

The spelling of 21644252 in words is "twenty-one million, six hundred forty-four thousand, two hundred fifty-two".