21993872 has 10 divisors (see below), whose sum is σ = 42613158. Its totient is φ = 10996928.

The previous prime is 21993871. The next prime is 21993893. The reversal of 21993872 is 27839912.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16777216 + 5216656 = 4096^2 + 2284^2 .

It is not an unprimeable number, because it can be changed into a prime (21993871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 687293 + ... + 687324.

Almost surely, 2^21993872 is an apocalyptic number.

It is an amenable number.

21993872 is a deficient number, since it is larger than the sum of its proper divisors (20619286).

21993872 is a wasteful number, since it uses less digits than its factorization.

21993872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1374625 (or 1374619 counting only the distinct ones).

The product of its digits is 54432, while the sum is 41.

The square root of 21993872 is about 4689.7624673324. The cubic root of 21993872 is about 280.1779141389.

The spelling of 21993872 in words is "twenty-one million, nine hundred ninety-three thousand, eight hundred seventy-two".