195809 has 2 divisors, whose sum is σ = 195810. Its totient is φ = 195808.

The previous prime is 195791. The next prime is 195817. The reversal of 195809 is 908591.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 193600 + 2209 = 440^2 + 47^2 .

It is an emirp because it is prime and its reverse (908591) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-195809 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 195809.

It is not a weakly prime, because it can be changed into another prime (195869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97904 + 97905.

It is an arithmetic number, because the mean of its divisors is an integer number (97905).

2¹⁹⁵⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

195809 is a deficient number, since it is larger than the sum of its proper divisors (1).

195809 is an equidigital number, since it uses as much as digits as its factorization.

195809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3240, while the sum is 32.

The square root of 195809 is about 442.5031073337. The cubic root of 195809 is about 58.0689825285.

The spelling of 195809 in words is "one hundred ninety-five thousand, eight hundred nine".