The greatest number, you can express with the common symbols of Roman numerals is 3999, because you can only use the same symbol three times in a number. You can’t use four M’s to express the number 4000.
However, if you put a horizontal line above a symbol, it means that value of the symbol must be multiplied by 1000.
IV = 4
So the greatest value you can express in Roman numerals without using the horizontal line is:
MMMCMXCIX = 3999
The longest Roman numeral, if it depends on the number of symbols, is a number with 15 symbols:
MMMDCCCLXXXVIII = 3888
Sometimes the number 4 is wrongly written as IIII. The right way to write it is of course IV.
Officilaly the number zero doesn’t exist in the Roman numeral system. However, according to sources from Ancient Rome the term “Nulla” was used, which means “nothing”.
The use of Roman numerals today
Today Roman numerals are used for many purposes. Here are some examples.
- On buildings the year of construction is often written with Roman numerals.
- Names of monarchs and popes, like for instance Queen Elizabeth II of the United Kingdom or Pope Benedict XVI, contains Roman numerals.
- Clocks from the old days often have Roman numerals on their faces instead of Arabic numbers.
- Each volume of a series of books or journals are often numbered with Roman numerals.
- Sports events, like Superbowl or the Olympic Games, are named with Roman numerals. (For example, the Olympic Games in London in 2012 is called XXX Olympiad because it’s the 30th Olympic Games being held.)