21987572 has 24 divisors (see below), whose sum is σ = 39554760. Its totient is φ = 10690560.

The previous prime is 21987571. The next prime is 21987601. The reversal of 21987572 is 27578912.

It can be written as a sum of positive squares in 4 ways, for example, as 1430416 + 20557156 = 1196^2 + 4534^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987571) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23204 + ... + 24132.

It is an arithmetic number, because the mean of its divisors is an integer number (1648115).

Almost surely, 2^21987572 is an apocalyptic number.

It is an amenable number.

21987572 is a deficient number, since it is larger than the sum of its proper divisors (17567188).

21987572 is a wasteful number, since it uses less digits than its factorization.

21987572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1091 (or 1089 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 21987572 is about 4689.0907434171. The cubic root of 21987572 is about 280.1511598772.

The spelling of 21987572 in words is "twenty-one million, nine hundred eighty-seven thousand, five hundred seventy-two".