Number
420 in Roman numerals
420 is written CDXX
Type any other number or numeral below to convert it.
Above 3,999? Type the barred part in brackets, e.g. (IV)CC = 4,200.
How CDXX is built
Roman numerals are written one decimal place at a time, largest first.
- CDhundreds · 4C before D means 500 − 100 = 400. This saves writing CCCC.
- XXtens · 2X written 2 times: 2 × 10 = 20.
400 + 20 = 420
The pair CD uses subtraction: a smaller letter before a larger one is taken away from it. Only six pairs work this way: IV, IX, XL, XC, CD and CM. More on subtraction
Mistakes to avoid
- Not CCCCXX (6 letters). That adds everything up without subtraction. The Romans sometimes wrote numbers this way, and clocks still show 4 as IIII, but today CDXX (4 letters) is the standard.
- There's no letter for zero. The zero is simply left out, which is why 420 has 2 parts, not 3.
About the number 420
- 420 is even and can be split into prime factors: 2 × 2 × 3 × 5 × 7, or in Roman numerals II × II × III × V × VII.
- CDXX has 4 letters. 784 of the numbers up to 1,000 have longer numerals.
Counting from 411 to 420
Every number from 411 to 420 starts CDX (410); only the ending changes.
| Number | Roman numeral |
|---|---|
| 411 | CDXI |
| 412 | CDXII |
| 413 | CDXIII |
| 414 | CDXIV |
| 415 | CDXV |
| 416 | CDXVI |
| 417 | CDXVII |
| 418 | CDXVIII |
| 419 | CDXIX |
| 420 | CDXX |