2165809 has 2 divisors, whose sum is σ = 2165810. Its totient is φ = 2165808.

The previous prime is 2165773. The next prime is 2165819. The reversal of 2165809 is 9085612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1221025 + 944784 = 1105^2 + 972^2 .

It is a cyclic number.

It is not a de Polignac number, because 2165809 - 2¹¹ = 2163761 is a prime.

It is a nialpdrome in base 12.

It is not a weakly prime, because it can be changed into another prime (2165819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1082904 + 1082905.

It is an arithmetic number, because the mean of its divisors is an integer number (1082905).

2^2165809 is an apocalyptic number.

It is an amenable number.

2165809 is a deficient number, since it is larger than the sum of its proper divisors (1).

2165809 is an equidigital number, since it uses as much as digits as its factorization.

2165809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 2165809 is about 1471.6687806704. The cubic root of 2165809 is about 129.3818583340.

The spelling of 2165809 in words is "two million, one hundred sixty-five thousand, eight hundred nine".