81319391 has 2 divisors, whose sum is σ = 81319392. Its totient is φ = 81319390.

The previous prime is 81319387. The next prime is 81319397. The reversal of 81319391 is 19391318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81319391 - 2² = 81319387 is a prime.

It is a super-2 number, since 2×81319391² = 13225686705221762, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81319397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40659695 + 40659696.

It is an arithmetic number, because the mean of its divisors is an integer number (40659696).

Almost surely, 2^81319391 is an apocalyptic number.

81319391 is a deficient number, since it is larger than the sum of its proper divisors (1).

81319391 is an equidigital number, since it uses as much as digits as its factorization.

81319391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5832, while the sum is 35.

The square root of 81319391 is about 9017.7264873138. The cubic root of 81319391 is about 433.2428185041.

The spelling of 81319391 in words is "eighty-one million, three hundred nineteen thousand, three hundred ninety-one".