21999972 has 24 divisors (see below), whose sum is σ = 54353376. Its totient is φ = 6901888.

The previous prime is 21999917. The next prime is 21999973. The reversal of 21999972 is 27999912.

It is not an unprimeable number, because it can be changed into a prime (21999973) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 53718 + ... + 54125.

It is an arithmetic number, because the mean of its divisors is an integer number (2264724).

Almost surely, 2^21999972 is an apocalyptic number.

It is an amenable number.

21999972 is an abundant number, since it is smaller than the sum of its proper divisors (32353404).

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

21999972 is a wasteful number, since it uses less digits than its factorization.

21999972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107867 (or 107865 counting only the distinct ones).

The product of its digits is 183708, while the sum is 48.

The square root of 21999972 is about 4690.4127750125. The cubic root of 21999972 is about 280.2038141911.

The spelling of 21999972 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred seventy-two".