Numbers / 217

The Number 217

217 is composite: factorization 7 × 31. That gives 217 exactly 4 divisors: 1, 7, 31, 217. 217's proper divisors total just 39, 178 short of 217, the deficient case most of 217's neighbors share too. 217 has a digit sum of 10; for 217, the digital root works out to 1. 217: 7 all divide 217 evenly, out of 2-12. 217 is 11011001 in binary and D9 in hex; as a Roman numeral it's CCXVII.