686659 has 4 divisors (see below), whose sum is σ = 695016. Its totient is φ = 678304.

The previous prime is 686639. The next prime is 686669. The reversal of 686659 is 956686.

686659 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: 956686 = 2 ⋅478343.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-686659 is a prime.

It is a Duffinian number.

686659 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (686639) 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, 4054 + ... + 4219.

It is an arithmetic number, because the mean of its divisors is an integer number (173754).

2⁶⁸⁶⁶⁵⁹ is an apocalyptic number.

686659 is a deficient number, since it is larger than the sum of its proper divisors (8357).

686659 is an equidigital number, since it uses as much as digits as its factorization.

686659 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8356.

The product of its digits is 77760, while the sum is 40.

The square root of 686659 is about 828.6489003191. The cubic root of 686659 is about 88.2227055418. Note that the first 3 decimals are identical.

The spelling of 686659 in words is "six hundred eighty-six thousand, six hundred fifty-nine".