81396691 has 2 divisors, whose sum is σ = 81396692. Its totient is φ = 81396690.

The previous prime is 81396671. The next prime is 81396709. The reversal of 81396691 is 19669318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81396691 - 2¹³ = 81388499 is a prime.

It is not a weakly prime, because it can be changed into another prime (81396661) 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, 40698345 + 40698346.

It is an arithmetic number, because the mean of its divisors is an integer number (40698346).

Almost surely, 2^81396691 is an apocalyptic number.

81396691 is a deficient number, since it is larger than the sum of its proper divisors (1).

81396691 is an equidigital number, since it uses as much as digits as its factorization.

81396691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 43.

The square root of 81396691 is about 9022.0114719501. The cubic root of 81396691 is about 433.3800513076.

The spelling of 81396691 in words is "eighty-one million, three hundred ninety-six thousand, six hundred ninety-one".