91581 has 16 divisors (see below), whose sum is σ = 144000. Its totient is φ = 51744.

The previous prime is 91577. The next prime is 91583. The reversal of 91581 is 18519.

It is not a de Polignac number, because 91581 - 2² = 91577 is a prime.

It is a super-2 number, since 2×91581² = 16774159122, which contains 22 as substring.

91581 is a lucky number.

It is a nialpdrome in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91583) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 985 + ... + 1073.

It is an arithmetic number, because the mean of its divisors is an integer number (9000).

2⁹¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

91581 is a deficient number, since it is larger than the sum of its proper divisors (52419).

91581 is an equidigital number, since it uses as much as digits as its factorization.

91581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113 (or 99 counting only the distinct ones).

The product of its digits is 360, while the sum is 24.

The square root of 91581 is about 302.6235284970. The cubic root of 91581 is about 45.0749368695.

The spelling of 91581 in words is "ninety-one thousand, five hundred eighty-one".