91911581 has 2 divisors, whose sum is σ = 91911582. Its totient is φ = 91911580.

The previous prime is 91911577. The next prime is 91911629. The reversal of 91911581 is 18511919.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 91508356 + 403225 = 9566^2 + 635^2 .

It is a cyclic number.

It is not a de Polignac number, because 91911581 - 2² = 91911577 is a prime.

It is a super-2 number, since 2×91911581² = 16895477443839122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91911541) 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 as a sum of consecutive naturals, namely, 45955790 + 45955791.

It is an arithmetic number, because the mean of its divisors is an integer number (45955791).

Almost surely, 2^91911581 is an apocalyptic number.

It is an amenable number.

91911581 is a deficient number, since it is larger than the sum of its proper divisors (1).

91911581 is an equidigital number, since it uses as much as digits as its factorization.

91911581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 35.

The square root of 91911581 is about 9587.0527796607. The cubic root of 91911581 is about 451.2910758260.

The spelling of 91911581 in words is "ninety-one million, nine hundred eleven thousand, five hundred eighty-one".