21808867 has 2 divisors, whose sum is σ = 21808868. Its totient is φ = 21808866.

The previous prime is 21808861. The next prime is 21808879. The reversal of 21808867 is 76880812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21808867 - 2³ = 21808859 is a prime.

It is not a weakly prime, because it can be changed into another prime (21808861) 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, 10904433 + 10904434.

It is an arithmetic number, because the mean of its divisors is an integer number (10904434).

Almost surely, 2^21808867 is an apocalyptic number.

21808867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21808867 is an equidigital number, since it uses as much as digits as its factorization.

21808867 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43008, while the sum is 40.

The square root of 21808867 is about 4669.9964668081. The cubic root of 21808867 is about 279.3901138585.

The spelling of 21808867 in words is "twenty-one million, eight hundred eight thousand, eight hundred sixty-seven".