686666 has 4 divisors (see below), whose sum is σ = 1030002. Its totient is φ = 343332.

The previous prime is 686639. The next prime is 686669. The reversal of 686666 is 666686.

686666 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.

It can be written as a sum of positive squares in only one way, i.e., 461041 + 225625 = 679^2 + 475^2 .

686666 is a modest number, since divided by 6666 gives 68 as remainder.

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 as a sum of consecutive naturals, namely, 171665 + ... + 171668.

2⁶⁸⁶⁶⁶⁶ is an apocalyptic number.

686666 is a deficient number, since it is larger than the sum of its proper divisors (343336).

686666 is a wasteful number, since it uses less digits than its factorization.

686666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 343335.

The product of its digits is 62208, while the sum is 38.

The square root of 686666 is about 828.6531240513. The cubic root of 686666 is about 88.2230053300.

The spelling of 686666 in words is "six hundred eighty-six thousand, six hundred sixty-six".