Numbers / 261

The Number 261

261 is composite: factorization 3^2 × 29. That gives 261 exactly 6 divisors: 1, 3, 9, 29, 87, 261. 261's proper divisors total just 129, 132 short of 261, the deficient case most of 261's neighbors share too. 261 has a digit sum of 9; for 261, the digital root works out to 9. 261: 3, 9 all divide 261 evenly, out of 2-12. 261 is 100000101 in binary and 105 in hex; as a Roman numeral it's CCLXI.