856809 has 24 divisors (see below), whose sum is σ = 1327872. Its totient is φ = 531360.

The previous prime is 856799. The next prime is 856811. The reversal of 856809 is 908658.

856809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 856809 - 2⁸ = 856553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (856309) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10282 + ... + 10364.

It is an arithmetic number, because the mean of its divisors is an integer number (55328).

2⁸⁵⁶⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

856809 is a deficient number, since it is larger than the sum of its proper divisors (471063).

856809 is a wasteful number, since it uses less digits than its factorization.

856809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157 (or 154 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 856809 is about 925.6397787477. The cubic root of 856809 is about 94.9790905043.

The spelling of 856809 in words is "eight hundred fifty-six thousand, eight hundred nine".