XXXI
30 + 1 = 31
XXXI breaks down as XXX + I (XXX = 30, I = 1), which add up to 31.
XXXI breaks down as XXX + I (XXX = 30, I = 1), which add up to 31.
The number 31 is written XXXI 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.