685209 has 16 divisors (see below), whose sum is σ = 1061888. Its totient is φ = 384912.

The previous prime is 685199. The next prime is 685231. The reversal of 685209 is 902586.

685209 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 685209 - 2⁵ = 685177 is a prime.

It is a super-2 number, since 2×685209² = 939022747362, which contains 22 as substring.

It is a Duffinian number.

685209 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1164 + ... + 1650.

It is an arithmetic number, because the mean of its divisors is an integer number (66368).

2⁶⁸⁵²⁰⁹ is an apocalyptic number.

It is an amenable number.

685209 is a deficient number, since it is larger than the sum of its proper divisors (376679).

685209 is a wasteful number, since it uses less digits than its factorization.

685209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 564.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 685209 is about 827.7735197504. The cubic root of 685209 is about 88.1605625796.

The spelling of 685209 in words is "six hundred eighty-five thousand, two hundred nine".