91981031 has 2 divisors, whose sum is σ = 91981032. Its totient is φ = 91981030.

The previous prime is 91981027. The next prime is 91981039. The reversal of 91981031 is 13018919.

It is a weak prime.

It is an emirp because it is prime and its reverse (13018919) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91981031 - 2² = 91981027 is a prime.

It is a super-2 number, since 2×91981031² = 16921020127645922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91981039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45990515 + 45990516.

It is an arithmetic number, because the mean of its divisors is an integer number (45990516).

Almost surely, 2^91981031 is an apocalyptic number.

91981031 is a deficient number, since it is larger than the sum of its proper divisors (1).

91981031 is an equidigital number, since it uses as much as digits as its factorization.

91981031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 32.

The square root of 91981031 is about 9590.6741681698. The cubic root of 91981031 is about 451.4047150212.

The spelling of 91981031 in words is "ninety-one million, nine hundred eighty-one thousand, thirty-one".