81366839 has 2 divisors, whose sum is σ = 81366840. Its totient is φ = 81366838.

The previous prime is 81366787. The next prime is 81366871. The reversal of 81366839 is 93866318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81366839 - 2⁸ = 81366583 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81366839.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81366889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40683419 + 40683420.

It is an arithmetic number, because the mean of its divisors is an integer number (40683420).

Almost surely, 2^81366839 is an apocalyptic number.

81366839 is a deficient number, since it is larger than the sum of its proper divisors (1).

81366839 is an equidigital number, since it uses as much as digits as its factorization.

81366839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 186624, while the sum is 44.

The square root of 81366839 is about 9020.3569219849. The cubic root of 81366839 is about 433.3270645378.

The spelling of 81366839 in words is "eighty-one million, three hundred sixty-six thousand, eight hundred thirty-nine".