21986309 has 2 divisors, whose sum is σ = 21986310. Its totient is φ = 21986308.

The previous prime is 21986273. The next prime is 21986317. The reversal of 21986309 is 90368912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16120225 + 5866084 = 4015^2 + 2422^2 .

It is a cyclic number.

It is not a de Polignac number, because 21986309 - 2²⁰ = 20937733 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21986329) 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 as a sum of consecutive naturals, namely, 10993154 + 10993155.

It is an arithmetic number, because the mean of its divisors is an integer number (10993155).

Almost surely, 2^21986309 is an apocalyptic number.

It is an amenable number.

21986309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21986309 is an equidigital number, since it uses as much as digits as its factorization.

21986309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21986309 is about 4688.9560671860. The cubic root of 21986309 is about 280.1457956698.

The spelling of 21986309 in words is "twenty-one million, nine hundred eighty-six thousand, three hundred nine".