Numbers / 90

The Number 90

90 is composite: factorization 2 × 3^2 × 5. That gives 90 exactly 12 divisors: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90. 90's proper divisors total 144, 54 more than 90 itself, so 90 is abundant. 90 has a digit sum of 9; for 90, the digital root works out to 9. 90: 2, 3, 5, 6, 9, 10 all divide 90 evenly, out of 2-12. 90 is 1011010 in binary and 5A in hex; as a Roman numeral it's XC.