Numbers / 861

The Number 861

861 is composite: factorization 3 × 7 × 41. That gives 861 exactly 8 divisors: 1, 3, 7, 21, 41, 123, 287, 861. 861's proper divisors total just 483, 378 short of 861, the deficient case most of 861's neighbors share too. 861 is also the 41st triangular number, the sum of 1 through 41. 861 has a digit sum of 15; for 861, the digital root works out to 6. 861: 3, 7 all divide 861 evenly, out of 2-12. 861 is 1101011101 in binary and 35D in hex; as a Roman numeral it's DCCCLXI.