686209 has 2 divisors, whose sum is σ = 686210. Its totient is φ = 686208.

The previous prime is 686201. The next prime is 686267. The reversal of 686209 is 902686.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 685584 + 625 = 828^2 + 25^2 .

It is a cyclic number.

It is not a de Polignac number, because 686209 - 2³ = 686201 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (686201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343104 + 343105.

It is an arithmetic number, because the mean of its divisors is an integer number (343105).

2⁶⁸⁶²⁰⁹ is an apocalyptic number.

It is an amenable number.

686209 is a deficient number, since it is larger than the sum of its proper divisors (1).

686209 is an equidigital number, since it uses as much as digits as its factorization.

686209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 686209 is about 828.3773294822. The cubic root of 686209 is about 88.2034291648.

The spelling of 686209 in words is "six hundred eighty-six thousand, two hundred nine".