117991 has 2 divisors, whose sum is σ = 117992. Its totient is φ = 117990.

The previous prime is 117989. The next prime is 118033. The reversal of 117991 is 199711.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 117991 - 2¹ = 117989 is a prime.

Together with 117989, it forms a pair of twin primes.

It is a zygodrome in base 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (117911) 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 as a sum of consecutive naturals, namely, 58995 + 58996.

It is an arithmetic number, because the mean of its divisors is an integer number (58996).

2¹¹⁷⁹⁹¹ is an apocalyptic number.

117991 is a deficient number, since it is larger than the sum of its proper divisors (1).

117991 is an equidigital number, since it uses as much as digits as its factorization.

117991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 567, while the sum is 28.

The square root of 117991 is about 343.4981804901. The cubic root of 117991 is about 49.0474342832.

The spelling of 117991 in words is "one hundred seventeen thousand, nine hundred ninety-one".