21808967 has 2 divisors, whose sum is σ = 21808968. Its totient is φ = 21808966.

The previous prime is 21808939. The next prime is 21808993. The reversal of 21808967 is 76980812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21808967 - 2⁸ = 21808711 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21808867) 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, 10904483 + 10904484.

It is an arithmetic number, because the mean of its divisors is an integer number (10904484).

Almost surely, 2^21808967 is an apocalyptic number.

21808967 is a deficient number, since it is larger than the sum of its proper divisors (1).

21808967 is an equidigital number, since it uses as much as digits as its factorization.

21808967 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21808967 is about 4670.0071734420. The cubic root of 21808967 is about 279.3905408862.

The spelling of 21808967 in words is "twenty-one million, eight hundred eight thousand, nine hundred sixty-seven".