85991 has 2 divisors, whose sum is σ = 85992. Its totient is φ = 85990.

The previous prime is 85933. The next prime is 85999. The reversal of 85991 is 19958.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 85991 - 2¹⁰ = 84967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85999) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42995 + 42996.

It is an arithmetic number, because the mean of its divisors is an integer number (42996).

2⁸⁵⁹⁹¹ is an apocalyptic number.

85991 is a deficient number, since it is larger than the sum of its proper divisors (1).

85991 is an equidigital number, since it uses as much as digits as its factorization.

85991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3240, while the sum is 32.

The square root of 85991 is about 293.2422206982. The cubic root of 85991 is about 44.1385098015.

The spelling of 85991 in words is "eighty-five thousand, nine hundred ninety-one".