21107839 has 2 divisors, whose sum is σ = 21107840. Its totient is φ = 21107838.

The previous prime is 21107791. The next prime is 21107851. The reversal of 21107839 is 93870112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21107839 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21107839.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21107239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553919 + 10553920.

It is an arithmetic number, because the mean of its divisors is an integer number (10553920).

Almost surely, 2^21107839 is an apocalyptic number.

21107839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21107839 is an equidigital number, since it uses as much as digits as its factorization.

21107839 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21107839 is about 4594.3268277300. The cubic root of 21107839 is about 276.3638649379.

The spelling of 21107839 in words is "twenty-one million, one hundred seven thousand, eight hundred thirty-nine".