21911291 has 2 divisors, whose sum is σ = 21911292. Its totient is φ = 21911290.

The previous prime is 21911273. The next prime is 21911297. The reversal of 21911291 is 19211912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21911291 - 2¹⁴ = 21894907 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21911291.

It is not a weakly prime, because it can be changed into another prime (21911297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10955645 + 10955646.

It is an arithmetic number, because the mean of its divisors is an integer number (10955646).

Almost surely, 2^21911291 is an apocalyptic number.

21911291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21911291 is an equidigital number, since it uses as much as digits as its factorization.

21911291 is an evil number, because the sum of its binary digits is even.

The product of its digits is 324, while the sum is 26.

The square root of 21911291 is about 4680.9497967827. The cubic root of 21911291 is about 279.8268104154.

The spelling of 21911291 in words is "twenty-one million, nine hundred eleven thousand, two hundred ninety-one".