21097291 has 2 divisors, whose sum is σ = 21097292. Its totient is φ = 21097290.

The previous prime is 21097283. The next prime is 21097331. The reversal of 21097291 is 19279012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21097291 - 2³ = 21097283 is a prime.

It is not a weakly prime, because it can be changed into another prime (21097231) 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, 10548645 + 10548646.

It is an arithmetic number, because the mean of its divisors is an integer number (10548646).

Almost surely, 2^21097291 is an apocalyptic number.

21097291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21097291 is an equidigital number, since it uses as much as digits as its factorization.

21097291 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21097291 is about 4593.1787467940. The cubic root of 21097291 is about 276.3178224581.

The spelling of 21097291 in words is "twenty-one million, ninety-seven thousand, two hundred ninety-one".