685840 has 20 divisors (see below), whose sum is σ = 1594764. Its totient is φ = 274304.

The previous prime is 685819. The next prime is 685849. The reversal of 685840 is 48586.

It can be written as a sum of positive squares in 2 ways, for example, as 234256 + 451584 = 484^2 + 672^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (685849) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4207 + ... + 4366.

2⁶⁸⁵⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

685840 is an abundant number, since it is smaller than the sum of its proper divisors (908924).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

685840 is a wasteful number, since it uses less digits than its factorization.

685840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8586 (or 8580 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 685840 is about 828.1545749436. The cubic root of 685840 is about 88.1876162463.

The spelling of 685840 in words is "six hundred eighty-five thousand, eight hundred forty".