165691 has 4 divisors (see below), whose sum is σ = 168232. Its totient is φ = 163152.

The previous prime is 165673. The next prime is 165701. The reversal of 165691 is 196561.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 165691 - 2¹¹ = 163643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1170 + ... + 1303.

It is an arithmetic number, because the mean of its divisors is an integer number (42058).

2¹⁶⁵⁶⁹¹ is an apocalyptic number.

165691 is a deficient number, since it is larger than the sum of its proper divisors (2541).

165691 is an equidigital number, since it uses as much as digits as its factorization.

165691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2540.

The product of its digits is 1620, while the sum is 28.

The square root of 165691 is about 407.0515937814. The cubic root of 165691 is about 54.9245245731.

The spelling of 165691 in words is "one hundred sixty-five thousand, six hundred ninety-one".