91781977391 has 16 divisors (see below), whose sum is σ = 104583491040. Its totient is φ = 79846871040.

The previous prime is 91781977387. The next prime is 91781977409. The reversal of 91781977391 is 19377918719.

It is a cyclic number.

It is not a de Polignac number, because 91781977391 - 2² = 91781977387 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91781977321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 914990 + ... + 1010331.

It is an arithmetic number, because the mean of its divisors is an integer number (6536468190).

Almost surely, 2^91781977391 is an apocalyptic number.

91781977391 is a deficient number, since it is larger than the sum of its proper divisors (12801513649).

91781977391 is a wasteful number, since it uses less digits than its factorization.

91781977391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1925546.

The product of its digits is 6001128, while the sum is 62.

The spelling of 91781977391 in words is "ninety-one billion, seven hundred eighty-one million, nine hundred seventy-seven thousand, three hundred ninety-one".