Numbers / 665

The Number 665

665 is composite: factorization 5 × 7 × 19. That gives 665 exactly 8 divisors: 1, 5, 7, 19, 35, 95, 133, 665. 665's proper divisors total just 295, 370 short of 665, the deficient case most of 665's neighbors share too. 665 has a digit sum of 17; for 665, the digital root works out to 8. 665: 5, 7 all divide 665 evenly, out of 2-12. 665 is 1010011001 in binary and 299 in hex; as a Roman numeral it's DCLXV.