91816591 has 4 divisors (see below), whose sum is σ = 92174112. Its totient is φ = 91459072.

The previous prime is 91816579. The next prime is 91816603. The reversal of 91816591 is 19561819.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19561819 = 137 ⋅142787.

It is an interprime number because it is at equal distance from previous prime (91816579) and next prime (91816603).

It is a cyclic number.

It is not a de Polignac number, because 91816591 - 2⁵ = 91816559 is a prime.

It is a super-2 number, since 2×91816591² = 16860572765722562, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91816891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178375 + ... + 178888.

It is an arithmetic number, because the mean of its divisors is an integer number (23043528).

Almost surely, 2^91816591 is an apocalyptic number.

91816591 is a deficient number, since it is larger than the sum of its proper divisors (357521).

91816591 is a wasteful number, since it uses less digits than its factorization.

91816591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 357520.

The product of its digits is 19440, while the sum is 40.

The square root of 91816591 is about 9582.0974217548. The cubic root of 91816591 is about 451.1355534740.

The spelling of 91816591 in words is "ninety-one million, eight hundred sixteen thousand, five hundred ninety-one".