21318839 has 2 divisors, whose sum is σ = 21318840. Its totient is φ = 21318838.

The previous prime is 21318821. The next prime is 21318859. The reversal of 21318839 is 93881312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21318839 - 2¹² = 21314743 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21318799 and 21318808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21318859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10659419 + 10659420.

It is an arithmetic number, because the mean of its divisors is an integer number (10659420).

Almost surely, 2^21318839 is an apocalyptic number.

21318839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21318839 is an equidigital number, since it uses as much as digits as its factorization.

21318839 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 21318839 is about 4617.2328293037. The cubic root of 21318839 is about 277.2816842008.

The spelling of 21318839 in words is "twenty-one million, three hundred eighteen thousand, eight hundred thirty-nine".