165409 has 4 divisors (see below), whose sum is σ = 166320. Its totient is φ = 164500.

The previous prime is 165397. The next prime is 165437. The reversal of 165409 is 904561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 904561 = 7 ⋅129223.

It is a cyclic number.

It is not a de Polignac number, because 165409 - 2¹³ = 157217 is a prime.

It is a Duffinian number.

165409 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (165449) 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, 79 + ... + 580.

It is an arithmetic number, because the mean of its divisors is an integer number (41580).

2¹⁶⁵⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

165409 is a deficient number, since it is larger than the sum of its proper divisors (911).

165409 is an equidigital number, since it uses as much as digits as its factorization.

165409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 910.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 165409 is about 406.7050528331. The cubic root of 165409 is about 54.8933470372.

The spelling of 165409 in words is "one hundred sixty-five thousand, four hundred nine".