21251244 has 48 divisors (see below), whose sum is σ = 58505216. Its totient is φ = 5875200.

The previous prime is 21251239. The next prime is 21251257. The reversal of 21251244 is 44215212.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21251244.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1477 + ... + 6684.

Almost surely, 2^21251244 is an apocalyptic number.

It is an amenable number.

21251244 is an abundant number, since it is smaller than the sum of its proper divisors (37253972).

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

21251244 is a wasteful number, since it uses less digits than its factorization.

21251244 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8206 (or 8204 counting only the distinct ones).

The product of its digits is 640, while the sum is 21.

The square root of 21251244 is about 4609.9071574165. The cubic root of 21251244 is about 276.9883177008.

Adding to 21251244 its reverse (44215212), we get a palindrome (65466456).

The spelling of 21251244 in words is "twenty-one million, two hundred fifty-one thousand, two hundred forty-four".