21311393 has 2 divisors, whose sum is σ = 21311394. Its totient is φ = 21311392.

The previous prime is 21311347. The next prime is 21311399. The reversal of 21311393 is 39311312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18515809 + 2795584 = 4303^2 + 1672^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311393 - 2⁸ = 21311137 is a prime.

It is not a weakly prime, because it can be changed into another prime (21311399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655696 + 10655697.

It is an arithmetic number, because the mean of its divisors is an integer number (10655697).

Almost surely, 2^21311393 is an apocalyptic number.

It is an amenable number.

21311393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311393 is an equidigital number, since it uses as much as digits as its factorization.

21311393 is an evil number, because the sum of its binary digits is even.

The product of its digits is 486, while the sum is 23.

The square root of 21311393 is about 4616.4264317760. The cubic root of 21311393 is about 277.2493985177.

The spelling of 21311393 in words is "twenty-one million, three hundred eleven thousand, three hundred ninety-three".