809891 has 2 divisors, whose sum is σ = 809892. Its totient is φ = 809890.

The previous prime is 809869. The next prime is 809903. The reversal of 809891 is 198908.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 809891 - 2⁶ = 809827 is a prime.

It is not a weakly prime, because it can be changed into another prime (809801) 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, 404945 + 404946.

It is an arithmetic number, because the mean of its divisors is an integer number (404946).

2⁸⁰⁹⁸⁹¹ is an apocalyptic number.

809891 is a deficient number, since it is larger than the sum of its proper divisors (1).

809891 is an equidigital number, since it uses as much as digits as its factorization.

809891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 35.

The square root of 809891 is about 899.9394424071. The cubic root of 809891 is about 93.2127936535.

The spelling of 809891 in words is "eight hundred nine thousand, eight hundred ninety-one".