XIII
10 + 3 = 13
XIII breaks down as X + III (X = 10, III = 3), which add up to 13.
XIII breaks down as X + III (X = 10, III = 3), which add up to 13.
The number 13 is written XIII 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.