91931209791 has 16 divisors (see below), whose sum is σ = 129831253344. Its totient is φ = 57661876224.

The previous prime is 91931209787. The next prime is 91931209831. The reversal of 91931209791 is 19790213919.

It is not a de Polignac number, because 91931209791 - 2² = 91931209787 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91931209291) 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, 173656 + ... + 462621.

It is an arithmetic number, because the mean of its divisors is an integer number (8114453334).

Almost surely, 2^91931209791 is an apocalyptic number.

91931209791 is a deficient number, since it is larger than the sum of its proper divisors (37900043553).

91931209791 is a wasteful number, since it uses less digits than its factorization.

91931209791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 639130.

The product of its (nonzero) digits is 275562, while the sum is 51.

The spelling of 91931209791 in words is "ninety-one billion, nine hundred thirty-one million, two hundred nine thousand, seven hundred ninety-one".