21339391 has 2 divisors, whose sum is σ = 21339392. Its totient is φ = 21339390.

The previous prime is 21339379. The next prime is 21339397. The reversal of 21339391 is 19393312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21339391 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21339397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10669695 + 10669696.

It is an arithmetic number, because the mean of its divisors is an integer number (10669696).

Almost surely, 2^21339391 is an apocalyptic number.

21339391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21339391 is an equidigital number, since it uses as much as digits as its factorization.

21339391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4374, while the sum is 31.

The square root of 21339391 is about 4619.4578686248. The cubic root of 21339391 is about 277.3707582027.

The spelling of 21339391 in words is "twenty-one million, three hundred thirty-nine thousand, three hundred ninety-one".