21364591 has 2 divisors, whose sum is σ = 21364592. Its totient is φ = 21364590.

The previous prime is 21364547. The next prime is 21364601. The reversal of 21364591 is 19546312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21364591 - 2⁷ = 21364463 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21364501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682295 + 10682296.

It is an arithmetic number, because the mean of its divisors is an integer number (10682296).

Almost surely, 2^21364591 is an apocalyptic number.

21364591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21364591 is an equidigital number, since it uses as much as digits as its factorization.

21364591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 31.

The square root of 21364591 is about 4622.1846566315. The cubic root of 21364591 is about 277.4798989850.

The spelling of 21364591 in words is "twenty-one million, three hundred sixty-four thousand, five hundred ninety-one".