21624943 has 4 divisors (see below), whose sum is σ = 21634488. Its totient is φ = 21615400.

The previous prime is 21624937. The next prime is 21624947. The reversal of 21624943 is 34942612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21624943 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21624947) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 780 + ... + 6622.

It is an arithmetic number, because the mean of its divisors is an integer number (5408622).

Almost surely, 2^21624943 is an apocalyptic number.

21624943 is a deficient number, since it is larger than the sum of its proper divisors (9545).

21624943 is an equidigital number, since it uses as much as digits as its factorization.

21624943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9544.

The product of its digits is 10368, while the sum is 31.

The square root of 21624943 is about 4650.2626807526. The cubic root of 21624943 is about 278.6024879930.

The spelling of 21624943 in words is "twenty-one million, six hundred twenty-four thousand, nine hundred forty-three".