166991 has 16 divisors (see below), whose sum is σ = 207360. Its totient is φ = 132480.

The previous prime is 166987. The next prime is 167009. The reversal of 166991 is 199661.

It is a happy number.

166991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 166991 - 2² = 166987 is a prime.

166991 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 166991.

It is not an unprimeable number, because it can be changed into a prime (166931) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3530 + ... + 3576.

It is an arithmetic number, because the mean of its divisors is an integer number (12960).

2¹⁶⁶⁹⁹¹ is an apocalyptic number.

166991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

166991 is a deficient number, since it is larger than the sum of its proper divisors (40369).

166991 is a wasteful number, since it uses less digits than its factorization.

166991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94.

The product of its digits is 2916, while the sum is 32.

The square root of 166991 is about 408.6453229880. The cubic root of 166991 is about 55.0677951865.

It can be divided in two parts, 16 and 6991, that added together give a palindrome (7007).

The spelling of 166991 in words is "one hundred sixty-six thousand, nine hundred ninety-one".