165591 has 8 divisors (see below), whose sum is σ = 245360. Its totient is φ = 110376.

The previous prime is 165589. The next prime is 165601. The reversal of 165591 is 195561.

165591 is a `hidden beast` number, since 1 + 655 + 9 + 1 = 666.

It is not a de Polignac number, because 165591 - 2¹ = 165589 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 6133 = 165591 / (1 + 6 + 5 + 5 + 9 + 1).

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3040 + ... + 3093.

It is an arithmetic number, because the mean of its divisors is an integer number (30670).

2¹⁶⁵⁵⁹¹ is an apocalyptic number.

165591 is a deficient number, since it is larger than the sum of its proper divisors (79769).

165591 is an equidigital number, since it uses as much as digits as its factorization.

165591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6142 (or 6136 counting only the distinct ones).

The product of its digits is 1350, while the sum is 27.

The square root of 165591 is about 406.9287406906. The cubic root of 165591 is about 54.9134727602.

The spelling of 165591 in words is "one hundred sixty-five thousand, five hundred ninety-one".