21129944 has 16 divisors (see below), whose sum is σ = 43220520. Its totient is φ = 9604480.

The previous prime is 21129943. The next prime is 21129947. The reversal of 21129944 is 44992112.

It is a self number, because there is not a number n which added to its sum of digits gives 21129944.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21129943) by changing a digit.

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, 119969 + ... + 120144.

Almost surely, 2^21129944 is an apocalyptic number.

It is an amenable number.

21129944 is an abundant number, since it is smaller than the sum of its proper divisors (22090576).

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

21129944 is a wasteful number, since it uses less digits than its factorization.

21129944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240130 (or 240126 counting only the distinct ones).

The product of its digits is 5184, while the sum is 32.

The square root of 21129944 is about 4596.7318825444. The cubic root of 21129944 is about 276.4603044950.

The spelling of 21129944 in words is "twenty-one million, one hundred twenty-nine thousand, nine hundred forty-four".