21644272 has 20 divisors (see below), whose sum is σ = 45162040. Its totient is φ = 9989568.

The previous prime is 21644267. The next prime is 21644303. The reversal of 21644272 is 27244612.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21644272.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51822 + ... + 52237.

It is an arithmetic number, because the mean of its divisors is an integer number (2258102).

Almost surely, 2^21644272 is an apocalyptic number.

It is an amenable number.

21644272 is an abundant number, since it is smaller than the sum of its proper divisors (23517768).

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

21644272 is a wasteful number, since it uses less digits than its factorization.

21644272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104080 (or 104074 counting only the distinct ones).

The product of its digits is 5376, while the sum is 28.

The square root of 21644272 is about 4652.3404862499. The cubic root of 21644272 is about 278.6854709298.

Adding to 21644272 its reverse (27244612), we get a palindrome (48888884).

The spelling of 21644272 in words is "twenty-one million, six hundred forty-four thousand, two hundred seventy-two".