169991 has 2 divisors, whose sum is σ = 169992. Its totient is φ = 169990.

The previous prime is 169987. The next prime is 170003. The reversal of 169991 is 199961.

It is a weak prime.

It is an emirp because it is prime and its reverse (199961) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 169991 - 2² = 169987 is a prime.

It is a plaindrome in base 15.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (169951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 84995 + 84996.

It is an arithmetic number, because the mean of its divisors is an integer number (84996).

2¹⁶⁹⁹⁹¹ is an apocalyptic number.

169991 is a deficient number, since it is larger than the sum of its proper divisors (1).

169991 is an equidigital number, since it uses as much as digits as its factorization.

169991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4374, while the sum is 35.

The square root of 169991 is about 412.2996483142. The cubic root of 169991 is about 55.3956049635.

The spelling of 169991 in words is "one hundred sixty-nine thousand, nine hundred ninety-one".