21620724 has 12 divisors (see below), whose sum is σ = 50448384. Its totient is φ = 7206904.

The previous prime is 21620723. The next prime is 21620737. The reversal of 21620724 is 42702612.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21620694 and 21620703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620723) 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, 900852 + ... + 900875.

It is an arithmetic number, because the mean of its divisors is an integer number (4204032).

Almost surely, 2^21620724 is an apocalyptic number.

It is an amenable number.

21620724 is an abundant number, since it is smaller than the sum of its proper divisors (28827660).

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

21620724 is a wasteful number, since it uses less digits than its factorization.

21620724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1801734 (or 1801732 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 21620724 is about 4649.8090283365. The cubic root of 21620724 is about 278.5843684794.

The spelling of 21620724 in words is "twenty-one million, six hundred twenty thousand, seven hundred twenty-four".