21840989 has 8 divisors (see below), whose sum is σ = 22801368. Its totient is φ = 20900160.

The previous prime is 21840977. The next prime is 21840991. The reversal of 21840989 is 98904812.

It can be written as a sum of positive squares in 4 ways, for example, as 3496900 + 18344089 = 1870^2 + 4283^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21840989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21840919) 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, 2582 + ... + 7095.

It is an arithmetic number, because the mean of its divisors is an integer number (2850171).

Almost surely, 2^21840989 is an apocalyptic number.

It is an amenable number.

21840989 is a deficient number, since it is larger than the sum of its proper divisors (960379).

21840989 is an equidigital number, since it uses as much as digits as its factorization.

21840989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9775.

The product of its (nonzero) digits is 41472, while the sum is 41.

The square root of 21840989 is about 4673.4343902531. The cubic root of 21840989 is about 279.5272166046.

The spelling of 21840989 in words is "twenty-one million, eight hundred forty thousand, nine hundred eighty-nine".