809 has 2 divisors, whose sum is σ = 810. Its totient is φ = 808.

The previous prime is 797. The next prime is 811. The reversal of 809 is 908.

809 is nontrivially palindromic in base 11 and base 12.

809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

809 is an esthetic number in base 11, because in such base its adjacent digits differ by 1.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 784 + 25 = 28^2 + 5^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^{k}-809 is a prime.

It is a Sophie Germain prime.

Together with 811, it forms a pair of twin primes.

It is a Chen prime.

It is a magnanimous number.

809 is an undulating number in base 11 and base 12.

809 is a modest number, since divided by 9 gives 8 as remainder.

It is a Curzon number.

It is a plaindrome in base 7 and base 15.

It is not a weakly prime, because it can be changed into another prime (829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404 + 405.

It is an arithmetic number, because the mean of its divisors is an integer number (405).

It is an amenable number.

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

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

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

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 809 is about 28.4429253067. The cubic root of 809 is about 9.3178598486.

Subtracting from 809 its product of nonzero digits (72), we obtain a palindrome (737).

Subtracting 809 from its reverse (908), we obtain a palindrome (99).

The spelling of 809 in words is "eight hundred nine", and thus it is an aban number and an oban number.

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