21135839 has 2 divisors, whose sum is σ = 21135840. Its totient is φ = 21135838.

The previous prime is 21135823. The next prime is 21135841. The reversal of 21135839 is 93853112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21135839 - 2⁴ = 21135823 is a prime.

Together with 21135841, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21135889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567919 + 10567920.

It is an arithmetic number, because the mean of its divisors is an integer number (10567920).

Almost surely, 2^21135839 is an apocalyptic number.

21135839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135839 is an equidigital number, since it uses as much as digits as its factorization.

21135839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 32.

The square root of 21135839 is about 4597.3730542561. The cubic root of 21135839 is about 276.4860118034.

The spelling of 21135839 in words is "twenty-one million, one hundred thirty-five thousand, eight hundred thirty-nine".