91991117 has 2 divisors, whose sum is σ = 91991118. Its totient is φ = 91991116.

The previous prime is 91991113. The next prime is 91991171. The reversal of 91991117 is 71119919.

Together with next prime (91991171) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54671236 + 37319881 = 7394^2 + 6109^2 .

It is a cyclic number.

It is not a de Polignac number, because 91991117 - 2² = 91991113 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91991113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45995558 + 45995559.

It is an arithmetic number, because the mean of its divisors is an integer number (45995559).

Almost surely, 2^91991117 is an apocalyptic number.

It is an amenable number.

91991117 is a deficient number, since it is larger than the sum of its proper divisors (1).

91991117 is an equidigital number, since it uses as much as digits as its factorization.

91991117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5103, while the sum is 38.

The square root of 91991117 is about 9591.1999770623. The cubic root of 91991117 is about 451.4212137185.

The spelling of 91991117 in words is "ninety-one million, nine hundred ninety-one thousand, one hundred seventeen".