81793891391 has 2 divisors, whose sum is σ = 81793891392. Its totient is φ = 81793891390.

The previous prime is 81793891349. The next prime is 81793891457. The reversal of 81793891391 is 19319839718.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81793891391 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81793891391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81793891591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40896945695 + 40896945696.

It is an arithmetic number, because the mean of its divisors is an integer number (40896945696).

Almost surely, 2^81793891391 is an apocalyptic number.

81793891391 is a deficient number, since it is larger than the sum of its proper divisors (1).

81793891391 is an equidigital number, since it uses as much as digits as its factorization.

81793891391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2939328, while the sum is 59.

The spelling of 81793891391 in words is "eighty-one billion, seven hundred ninety-three million, eight hundred ninety-one thousand, three hundred ninety-one".