Numbers / 681

The Number 681

681 is composite: factorization 3 × 227. That gives 681 exactly 4 divisors: 1, 3, 227, 681. 681's proper divisors total just 231, 450 short of 681, the deficient case most of 681's neighbors share too. 681 has a digit sum of 15; for 681, the digital root works out to 6. 681: 3 all divide 681 evenly, out of 2-12. 681 is 1010101001 in binary and 2A9 in hex; as a Roman numeral it's DCLXXXI.