21945889 has 4 divisors (see below), whose sum is σ = 25081024. Its totient is φ = 18810756.

The previous prime is 21945881. The next prime is 21945907. The reversal of 21945889 is 98854912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21945889 - 2³ = 21945881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21945881) 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 3 ways as a sum of consecutive naturals, for example, 1567557 + ... + 1567570.

It is an arithmetic number, because the mean of its divisors is an integer number (6270256).

Almost surely, 2^21945889 is an apocalyptic number.

It is an amenable number.

21945889 is a deficient number, since it is larger than the sum of its proper divisors (3135135).

21945889 is an equidigital number, since it uses as much as digits as its factorization.

21945889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3135134.

The product of its digits is 207360, while the sum is 46.

The square root of 21945889 is about 4684.6439565884. The cubic root of 21945889 is about 279.9740154458.

The spelling of 21945889 in words is "twenty-one million, nine hundred forty-five thousand, eight hundred eighty-nine".