91981231 has 2 divisors, whose sum is σ = 91981232. Its totient is φ = 91981230.

The previous prime is 91981217. The next prime is 91981249. The reversal of 91981231 is 13218919.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 91981231 - 2⁷ = 91981103 is a prime.

It is a super-3 number, since 3×91981231³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91981031) 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, 45990615 + 45990616.

It is an arithmetic number, because the mean of its divisors is an integer number (45990616).

Almost surely, 2^91981231 is an apocalyptic number.

91981231 is a deficient number, since it is larger than the sum of its proper divisors (1).

91981231 is an equidigital number, since it uses as much as digits as its factorization.

91981231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 34.

The square root of 91981231 is about 9590.6845949598. The cubic root of 91981231 is about 451.4050421933.

The spelling of 91981231 in words is "ninety-one million, nine hundred eighty-one thousand, two hundred thirty-one".