Numbers / 99

The Number 99

99 is composite: factorization 3^2 × 11. That gives 99 exactly 6 divisors: 1, 3, 9, 11, 33, 99. 99's proper divisors total just 57, 42 short of 99, the deficient case most of 99's neighbors share too. 99 is also a palindrome, since 99 reads identically forwards and backwards. 99 has a digit sum of 18; for 99, the digital root works out to 9. 99: 3, 9, 11 all divide 99 evenly, out of 2-12. 99 is 1100011 in binary and 63 in hex; as a Roman numeral it's XCIX.