809909 has 2 divisors, whose sum is σ = 809910. Its totient is φ = 809908.

The previous prime is 809903. The next prime is 809917. The reversal of 809909 is 909908.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 504100 + 305809 = 710^2 + 553^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-809909 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404954 + 404955.

It is an arithmetic number, because the mean of its divisors is an integer number (404955).

2⁸⁰⁹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

809909 is a deficient number, since it is larger than the sum of its proper divisors (1).

809909 is an equidigital number, since it uses as much as digits as its factorization.

809909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 809909 is about 899.9494430244. The cubic root of 809909 is about 93.2134842064.

Subtracting 809909 from its reverse (909908), we obtain a palindrome (99999).

The spelling of 809909 in words is "eight hundred nine thousand, nine hundred nine".