21866729 has 2 divisors, whose sum is σ = 21866730. Its totient is φ = 21866728.

The previous prime is 21866699. The next prime is 21866737. The reversal of 21866729 is 92766812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21641104 + 225625 = 4652^2 + 475^2 .

It is a cyclic number.

It is not a de Polignac number, because 21866729 - 2²⁰ = 20818153 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21866329) 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, 10933364 + 10933365.

It is an arithmetic number, because the mean of its divisors is an integer number (10933365).

Almost surely, 2^21866729 is an apocalyptic number.

It is an amenable number.

21866729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21866729 is an equidigital number, since it uses as much as digits as its factorization.

21866729 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 41.

The square root of 21866729 is about 4676.1874427786. The cubic root of 21866729 is about 279.6369827865.

The spelling of 21866729 in words is "twenty-one million, eight hundred sixty-six thousand, seven hundred twenty-nine".