Numbers / 686

The Number 686

686 is composite: factorization 2 × 7^3. That gives 686 exactly 8 divisors: 1, 2, 7, 14, 49, 98, 343, 686. 686's proper divisors total just 514, 172 short of 686, the deficient case most of 686's neighbors share too. 686 is also a palindrome, since 686 reads identically forwards and backwards. 686 has a digit sum of 20; for 686, the digital root works out to 2. 686: 2, 7 all divide 686 evenly, out of 2-12. 686 is 1010101110 in binary and 2AE in hex; as a Roman numeral it's DCLXXXVI.