165806209 has 2 divisors, whose sum is σ = 165806210. Its totient is φ = 165806208.

The previous prime is 165806161. The next prime is 165806231. The reversal of 165806209 is 902608561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 107329600 + 58476609 = 10360^2 + 7647^2 .

It is an emirp because it is prime and its reverse (902608561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 165806209 - 2¹⁵ = 165773441 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (165806239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82903104 + 82903105.

It is an arithmetic number, because the mean of its divisors is an integer number (82903105).

Almost surely, 2^165806209 is an apocalyptic number.

It is an amenable number.

165806209 is a deficient number, since it is larger than the sum of its proper divisors (1).

165806209 is an equidigital number, since it uses as much as digits as its factorization.

165806209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 165806209 is about 12876.5759812149. The cubic root of 165806209 is about 549.3725174495.

The spelling of 165806209 in words is "one hundred sixty-five million, eight hundred six thousand, two hundred nine".