91205857181 has 2 divisors, whose sum is σ = 91205857182. Its totient is φ = 91205857180.

The previous prime is 91205857129. The next prime is 91205857229. The reversal of 91205857181 is 18175850219.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47103757156 + 44102100025 = 217034^2 + 210005^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91205857181 is a prime.

It is a super-2 number, since 2×91205857181² (a number of 23 digits) contains 22 as substring.

It is a Sophie Germain 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 (91205857121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45602928590 + 45602928591.

It is an arithmetic number, because the mean of its divisors is an integer number (45602928591).

Almost surely, 2^91205857181 is an apocalyptic number.

It is an amenable number.

91205857181 is a deficient number, since it is larger than the sum of its proper divisors (1).

91205857181 is an equidigital number, since it uses as much as digits as its factorization.

91205857181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 201600, while the sum is 47.

The spelling of 91205857181 in words is "ninety-one billion, two hundred five million, eight hundred fifty-seven thousand, one hundred eighty-one".