206809 has 4 divisors (see below), whose sum is σ = 209716. Its totient is φ = 203904.

The previous prime is 206807. The next prime is 206813. The reversal of 206809 is 908602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 99225 + 107584 = 315^2 + 328^2 .

It is a cyclic number.

It is not a de Polignac number, because 206809 - 2¹ = 206807 is a prime.

It is an Ulam number.

It is a Duffinian number.

206809 is a lucky number.

It is a nialpdrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (206803) 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 in 3 ways as a sum of consecutive naturals, for example, 1344 + ... + 1489.

It is an arithmetic number, because the mean of its divisors is an integer number (52429).

2²⁰⁶⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

206809 is a deficient number, since it is larger than the sum of its proper divisors (2907).

206809 is an equidigital number, since it uses as much as digits as its factorization.

206809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2906.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 206809 is about 454.7625754171. The cubic root of 206809 is about 59.1366172435.

The spelling of 206809 in words is "two hundred six thousand, eight hundred nine".