XCIX
90 + 9 = 99
XCIX breaks down as XC + IX (XC = 90, IX = 9), which add up to 99. It uses subtractive notation: IX (10 - 1), XC (100 - 10).
XCIX breaks down as XC + IX (XC = 90, IX = 9), which add up to 99. It uses subtractive notation: IX (10 - 1), XC (100 - 10).
The number 99 is written XCIX in Roman numerals. Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500) and M (1000) — combined from largest to smallest, with subtractive pairs such as IV (4) and IX (9). Need another number? Use the Roman numeral converter or see the 1–100 chart.