Numbers / 669

The Number 669

669 is composite: factorization 3 × 223. That gives 669 exactly 4 divisors: 1, 3, 223, 669. 669's proper divisors total just 227, 442 short of 669, the deficient case most of 669's neighbors share too. 669 has a digit sum of 21; for 669, the digital root works out to 3. 669: 3 all divide 669 evenly, out of 2-12. 669 is 1010011101 in binary and 29D in hex; as a Roman numeral it's DCLXIX.