91138971691 has 4 divisors (see below), whose sum is σ = 91177219552. Its totient is φ = 91100723832.

The previous prime is 91138971689. The next prime is 91138971713. The reversal of 91138971691 is 19617983119.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 91138971691 - 2¹ = 91138971689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91138975691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19120356 + ... + 19125121.

It is an arithmetic number, because the mean of its divisors is an integer number (22794304888).

Almost surely, 2^91138971691 is an apocalyptic number.

91138971691 is a deficient number, since it is larger than the sum of its proper divisors (38247861).

91138971691 is a wasteful number, since it uses less digits than its factorization.

91138971691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38247860.

The product of its digits is 734832, while the sum is 55.

The spelling of 91138971691 in words is "ninety-one billion, one hundred thirty-eight million, nine hundred seventy-one thousand, six hundred ninety-one".