81333391 has 2 divisors, whose sum is σ = 81333392. Its totient is φ = 81333390.

The previous prime is 81333361. The next prime is 81333431. The reversal of 81333391 is 19333318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81333391 - 2¹⁵ = 81300623 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81333311) 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, 40666695 + 40666696.

It is an arithmetic number, because the mean of its divisors is an integer number (40666696).

Almost surely, 2^81333391 is an apocalyptic number.

81333391 is a deficient number, since it is larger than the sum of its proper divisors (1).

81333391 is an equidigital number, since it uses as much as digits as its factorization.

81333391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5832, while the sum is 31.

The square root of 81333391 is about 9018.5027027772. The cubic root of 81333391 is about 433.2676795340.

The spelling of 81333391 in words is "eighty-one million, three hundred thirty-three thousand, three hundred ninety-one".