686689 has 4 divisors (see below), whose sum is σ = 692224. Its totient is φ = 681156.

The previous prime is 686687. The next prime is 686723. The reversal of 686689 is 986686.

686689 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 a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 686689 - 2¹ = 686687 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (686687) 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, 2577 + ... + 2830.

It is an arithmetic number, because the mean of its divisors is an integer number (173056).

2⁶⁸⁶⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

686689 is a deficient number, since it is larger than the sum of its proper divisors (5535).

686689 is a wasteful number, since it uses less digits than its factorization.

686689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5534.

The product of its digits is 124416, while the sum is 43.

The square root of 686689 is about 828.6670018771. The cubic root of 686689 is about 88.2239903341.

The spelling of 686689 in words is "six hundred eighty-six thousand, six hundred eighty-nine".