165805 has 4 divisors (see below), whose sum is σ = 198972. Its totient is φ = 132640.

The previous prime is 165799. The next prime is 165811. The reversal of 165805 is 508561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 508561 = 43 ⋅11827.

It is an interprime number because it is at equal distance from previous prime (165799) and next prime (165811).

It can be written as a sum of positive squares in 2 ways, for example, as 116964 + 48841 = 342^2 + 221^2 .

It is not a de Polignac number, because 165805 - 2⁹ = 165293 is a prime.

It is a Duffinian number.

165805 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 165805.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16576 + ... + 16585.

It is an arithmetic number, because the mean of its divisors is an integer number (49743).

2¹⁶⁵⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

165805 is a deficient number, since it is larger than the sum of its proper divisors (33167).

165805 is an equidigital number, since it uses as much as digits as its factorization.

165805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33166.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 165805 is about 407.1916010922. The cubic root of 165805 is about 54.9371182170.

The spelling of 165805 in words is "one hundred sixty-five thousand, eight hundred five".