21985989 has 16 divisors (see below), whose sum is σ = 30120960. Its totient is φ = 14258160.

The previous prime is 21985979. The next prime is 21986009. The reversal of 21985989 is 98958912.

21985989 = 212² + 213² + ... + 422².

It is not a de Polignac number, because 21985989 - 2⁹ = 21985477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21985939) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29382 + ... + 30120.

It is an arithmetic number, because the mean of its divisors is an integer number (1882560).

Almost surely, 2^21985989 is an apocalyptic number.

It is an amenable number.

21985989 is a deficient number, since it is larger than the sum of its proper divisors (8134971).

21985989 is a wasteful number, since it uses less digits than its factorization.

21985989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1000.

The product of its digits is 466560, while the sum is 51.

The square root of 21985989 is about 4688.9219443279. The cubic root of 21985989 is about 280.1444365348.

The spelling of 21985989 in words is "twenty-one million, nine hundred eighty-five thousand, nine hundred eighty-nine".