165806161 has 2 divisors, whose sum is σ = 165806162. Its totient is φ = 165806160.

The previous prime is 165806159. The next prime is 165806209. The reversal of 165806161 is 161608561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 148840000 + 16966161 = 12200^2 + 4119^2 .

It is a cyclic number.

It is not a de Polignac number, because 165806161 - 2¹ = 165806159 is a prime.

Together with 165806159, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (165306161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82903080 + 82903081.

It is an arithmetic number, because the mean of its divisors is an integer number (82903081).

Almost surely, 2^165806161 is an apocalyptic number.

It is an amenable number.

165806161 is a deficient number, since it is larger than the sum of its proper divisors (1).

165806161 is an equidigital number, since it uses as much as digits as its factorization.

165806161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 165806161 is about 12876.5741173652. The cubic root of 165806161 is about 549.3724644360.

The spelling of 165806161 in words is "one hundred sixty-five million, eight hundred six thousand, one hundred sixty-one".