Numbers / 231

The Number 231

231 is composite: factorization 3 × 7 × 11. That gives 231 exactly 8 divisors: 1, 3, 7, 11, 21, 33, 77, 231. 231's proper divisors total just 153, 78 short of 231, the deficient case most of 231's neighbors share too. 231 is also the 21st triangular number, the sum of 1 through 21. 231 has a digit sum of 6; for 231, the digital root works out to 6. 231: 3, 7, 11 all divide 231 evenly, out of 2-12. 231 is 11100111 in binary and E7 in hex; as a Roman numeral it's CCXXXI.