Roman Numerals

We don’t hear much about Roman numerals these days, although we often see them – on clock faces and inscriptions, and on the copyright dates for tv programmes and films. Here are some interesting facts about Roman numerals:

• Roman numerals use only 7 symbols (I, V, X, L, C, D, M) compared with the 10 for Arabic numerals
• The largest number that can be represented in the standard Roman notation is 3,999 (MMMCMXCIX) because 4,000 would have to be MMMM – and four consequtive letters of the same type are not allowed. Most Romans probably did not need to go higher than this but when they did they made use of the vinculum – a horizontal line above one or more letters to indicate they should be multiplied by 1,000. So 4,000 becomes I̅ V̅.
• There is no symbol for zero in Roman numerals. Since the Romans used numbers for counting things, there was no need for zero – nothing to count!
• There is a neat function in Microsoft’s Excel that converts a number to Roman numerals – roman(2021) = MMXXI. This function supports several variants of Roman numerals but they seem to have been invented by the developer of the function – so stick to the default!
• Roman numerals can be converted back to Arabic numerals – arabic(MM) = 2000.