857809 has 2 divisors, whose sum is σ = 857810. Its totient is φ = 857808.

The previous prime is 857749. The next prime is 857821. The reversal of 857809 is 908758.

857809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 685584 + 172225 = 828^2 + 415^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-857809 is a prime.

It is a Chen prime.

857809 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (857839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428904 + 428905.

It is an arithmetic number, because the mean of its divisors is an integer number (428905).

2⁸⁵⁷⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

857809 is a deficient number, since it is larger than the sum of its proper divisors (1).

857809 is an equidigital number, since it uses as much as digits as its factorization.

857809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 857809 is about 926.1797881621. The cubic root of 857809 is about 95.0160268436.

Adding to 857809 its product of nonzero digits (20160), we get a square (877969 = 937²).

The spelling of 857809 in words is "eight hundred fifty-seven thousand, eight hundred nine".