Numbers / 225

The Number 225

225 is composite: factorization 3^2 × 5^2. That gives 225 exactly 9 divisors: 1, 3, 5, 9, 15, 25, 45, 75, 225. 225's proper divisors total just 178, 47 short of 225, the deficient case most of 225's neighbors share too. 225 is also a perfect square, since 15² = 225. 225 has a digit sum of 9; for 225, the digital root works out to 9. 225: 3, 5, 9 all divide 225 evenly, out of 2-12. 225 is 11100001 in binary and E1 in hex; as a Roman numeral it's CCXXV.