686665 has 16 divisors (see below), whose sum is σ = 983808. Its totient is φ = 449856.

The previous prime is 686639. The next prime is 686669. The reversal of 686665 is 566686.

686665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 686665 - 2¹¹ = 684617 is a prime.

It is not an unprimeable number, because it can be changed into a prime (686669) 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, 379 + ... + 1231.

It is an arithmetic number, because the mean of its divisors is an integer number (61488).

2⁶⁸⁶⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

686665 is a deficient number, since it is larger than the sum of its proper divisors (297143).

686665 is a wasteful number, since it uses less digits than its factorization.

686665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 888.

The product of its digits is 51840, while the sum is 37.

The square root of 686665 is about 828.6525206623. The cubic root of 686665 is about 88.2229625032. Note that the first 3 decimals are identical.

The spelling of 686665 in words is "six hundred eighty-six thousand, six hundred sixty-five".