168991 has 2 divisors, whose sum is σ = 168992. Its totient is φ = 168990.

The previous prime is 168977. The next prime is 169003. The reversal of 168991 is 199861.

168991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 168991 - 2⁷ = 168863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168901) 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, 84495 + 84496.

It is an arithmetic number, because the mean of its divisors is an integer number (84496).

2¹⁶⁸⁹⁹¹ is an apocalyptic number.

168991 is a deficient number, since it is larger than the sum of its proper divisors (1).

168991 is an equidigital number, since it uses as much as digits as its factorization.

168991 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 168991 is about 411.0851493304. The cubic root of 168991 is about 55.2867666801.

It can be divided in two parts, 16899 and 1, that added together give a square (16900 = 130²).

The spelling of 168991 in words is "one hundred sixty-eight thousand, nine hundred ninety-one".