21866189 has 2 divisors, whose sum is σ = 21866190. Its totient is φ = 21866188.

The previous prime is 21866137. The next prime is 21866209. The reversal of 21866189 is 98166812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20097289 + 1768900 = 4483^2 + 1330^2 .

It is a cyclic number.

It is not a de Polignac number, because 21866189 - 2²⁴ = 5088973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21866989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10933094 + 10933095.

It is an arithmetic number, because the mean of its divisors is an integer number (10933095).

Almost surely, 2^21866189 is an apocalyptic number.

It is an amenable number.

21866189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21866189 is an equidigital number, since it uses as much as digits as its factorization.

21866189 is an evil number, because the sum of its binary digits is even.

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

The square root of 21866189 is about 4676.1297030771. The cubic root of 21866189 is about 279.6346808843.

The spelling of 21866189 in words is "twenty-one million, eight hundred sixty-six thousand, one hundred eighty-nine".