21885917 has 2 divisors, whose sum is σ = 21885918. Its totient is φ = 21885916.

The previous prime is 21885893. The next prime is 21885937. The reversal of 21885917 is 71958812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12313081 + 9572836 = 3509^2 + 3094^2 .

It is a cyclic number.

It is not a de Polignac number, because 21885917 - 2¹⁸ = 21623773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21885937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10942958 + 10942959.

It is an arithmetic number, because the mean of its divisors is an integer number (10942959).

Almost surely, 2^21885917 is an apocalyptic number.

It is an amenable number.

21885917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21885917 is an equidigital number, since it uses as much as digits as its factorization.

21885917 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40320, while the sum is 41.

The square root of 21885917 is about 4678.2386642838. The cubic root of 21885917 is about 279.7187524579.

The spelling of 21885917 in words is "twenty-one million, eight hundred eighty-five thousand, nine hundred seventeen".