165209409 has 16 divisors (see below), whose sum is σ = 244981440. Its totient is φ = 110037600.

The previous prime is 165209357. The next prime is 165209431. The reversal of 165209409 is 904902561.

It is not a de Polignac number, because 165209409 - 2⁸ = 165209153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165209609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37069 + ... + 41285.

It is an arithmetic number, because the mean of its divisors is an integer number (15311340).

Almost surely, 2^165209409 is an apocalyptic number.

It is an amenable number.

165209409 is a deficient number, since it is larger than the sum of its proper divisors (79772031).

165209409 is a wasteful number, since it uses less digits than its factorization.

165209409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5677 (or 5671 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 165209409 is about 12853.3812282994. The cubic root of 165209409 is about 548.7125910610.

The spelling of 165209409 in words is "one hundred sixty-five million, two hundred nine thousand, four hundred nine".