810809 has 2 divisors, whose sum is σ = 810810. Its totient is φ = 810808.

The previous prime is 810791. The next prime is 810839. The reversal of 810809 is 908018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 426409 + 384400 = 653^2 + 620^2 .

It is a cyclic number.

It is not a de Polignac number, because 810809 - 2⁸ = 810553 is a prime.

It is a super-2 number, since 2×810809² = 1314822468962, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (810839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 405404 + 405405.

It is an arithmetic number, because the mean of its divisors is an integer number (405405).

2⁸¹⁰⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

810809 is a deficient number, since it is larger than the sum of its proper divisors (1).

810809 is an equidigital number, since it uses as much as digits as its factorization.

810809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 810809 is about 900.4493322781. The cubic root of 810809 is about 93.2479988166.

The spelling of 810809 in words is "eight hundred ten thousand, eight hundred nine".