686605 has 4 divisors (see below), whose sum is σ = 823932. Its totient is φ = 549280.

The previous prime is 686593. The next prime is 686611. The reversal of 686605 is 506686.

686605 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 506686 = 2 ⋅253343.

It can be written as a sum of positive squares in 2 ways, for example, as 443556 + 243049 = 666^2 + 493^2 .

It is not a de Polignac number, because 686605 - 2¹¹ = 684557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68656 + ... + 68665.

It is an arithmetic number, because the mean of its divisors is an integer number (205983).

2⁶⁸⁶⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

686605 is a deficient number, since it is larger than the sum of its proper divisors (137327).

686605 is a wasteful number, since it uses less digits than its factorization.

686605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137326.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 686605 is about 828.6163165181. The cubic root of 686605 is about 88.2203928213.

The spelling of 686605 in words is "six hundred eighty-six thousand, six hundred five".