21115439 has 2 divisors, whose sum is σ = 21115440. Its totient is φ = 21115438.

The previous prime is 21115429. The next prime is 21115453. The reversal of 21115439 is 93451112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21115439 - 2²⁰ = 20066863 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557719 + 10557720.

It is an arithmetic number, because the mean of its divisors is an integer number (10557720).

Almost surely, 2^21115439 is an apocalyptic number.

21115439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115439 is an equidigital number, since it uses as much as digits as its factorization.

21115439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 26.

The square root of 21115439 is about 4595.1538603185. The cubic root of 21115439 is about 276.3970297626.

The spelling of 21115439 in words is "twenty-one million, one hundred fifteen thousand, four hundred thirty-nine".