21900724 has 12 divisors (see below), whose sum is σ = 39261348. Its totient is φ = 10683200.

The previous prime is 21900691. The next prime is 21900737. The reversal of 21900724 is 42700912.

It can be written as a sum of positive squares in 2 ways, for example, as 4761124 + 17139600 = 2182^2 + 4140^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66607 + ... + 66934.

It is an arithmetic number, because the mean of its divisors is an integer number (3271779).

Almost surely, 2^21900724 is an apocalyptic number.

It is an amenable number.

21900724 is a deficient number, since it is larger than the sum of its proper divisors (17360624).

21900724 is a wasteful number, since it uses less digits than its factorization.

21900724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133586 (or 133584 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21900724 is about 4679.8209367453. The cubic root of 21900724 is about 279.7818198308.

The spelling of 21900724 in words is "twenty-one million, nine hundred thousand, seven hundred twenty-four".