21913691 has 2 divisors, whose sum is σ = 21913692. Its totient is φ = 21913690.

The previous prime is 21913679. The next prime is 21913709. The reversal of 21913691 is 19631912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21913691 - 2⁶ = 21913627 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21913601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10956845 + 10956846.

It is an arithmetic number, because the mean of its divisors is an integer number (10956846).

Almost surely, 2^21913691 is an apocalyptic number.

21913691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21913691 is an equidigital number, since it uses as much as digits as its factorization.

21913691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2916, while the sum is 32.

The square root of 21913691 is about 4681.2061479922. The cubic root of 21913691 is about 279.8370267589.

The spelling of 21913691 in words is "twenty-one million, nine hundred thirteen thousand, six hundred ninety-one".