21868081 has 2 divisors, whose sum is σ = 21868082. Its totient is φ = 21868080.

The previous prime is 21868043. The next prime is 21868087. The reversal of 21868081 is 18086812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17098225 + 4769856 = 4135^2 + 2184^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21868081 is a prime.

It is a super-2 number, since 2×21868081² = 956425933245122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21868087) 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, 10934040 + 10934041.

It is an arithmetic number, because the mean of its divisors is an integer number (10934041).

Almost surely, 2^21868081 is an apocalyptic number.

It is an amenable number.

21868081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21868081 is an equidigital number, since it uses as much as digits as its factorization.

21868081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6144, while the sum is 34.

The square root of 21868081 is about 4676.3320027560. The cubic root of 21868081 is about 279.6427459013.

The spelling of 21868081 in words is "twenty-one million, eight hundred sixty-eight thousand, eighty-one".