21957988 has 24 divisors (see below), whose sum is σ = 42812280. Its totient is φ = 9784320.

The previous prime is 21957979. The next prime is 21957989. The reversal of 21957988 is 88975912.

It can be written as a sum of positive squares in 4 ways, for example, as 3912484 + 18045504 = 1978^2 + 4248^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21957989) 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, 5773 + ... + 8788.

It is an arithmetic number, because the mean of its divisors is an integer number (1783845).

Almost surely, 2^21957988 is an apocalyptic number.

It is an amenable number.

21957988 is a deficient number, since it is larger than the sum of its proper divisors (20854292).

21957988 is a wasteful number, since it uses less digits than its factorization.

21957988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14607 (or 14605 counting only the distinct ones).

The product of its digits is 362880, while the sum is 49.

The square root of 21957988 is about 4685.9351254579. The cubic root of 21957988 is about 280.0254568691.

The spelling of 21957988 in words is "twenty-one million, nine hundred fifty-seven thousand, nine hundred eighty-eight".