**The Roman numeral for one million is the letter M with a horizontal line across the top.** This line, which is rarely used, indicates that the number should be multiplied by 1,000. Since the letter M represents 1,000, M plus the line represents 1,000 multiplied by 1,000.

Romans used a set of letters to represent numbers. In addition to M, the following letters were used:

- I: 1
- V: 5
- X: 10
- L: 50
- C: 100
- D: 500

Letters were combined to make other numbers, for example, LX represents 50 plus 10, or 60. Letters that are listed after a letter representing a larger number are added, while those that come before a larger number are subtracted. For example, VI represents 6, and IV represents 4.