421 in Roman Numerals
The number 421 is written CDXXI in Roman numerals. Click the numeral below to copy it, or use the converter to try any other number.
CDXXI uses 4 of the seven Roman numeral symbols and is 5 characters long.
Note the subtractive pair CD inside it: a smaller symbol placed before a larger one means subtract, which is why CD is 400 and not CCCC.
421 in Roman numerals
Also written in words as four hundred twenty-one, and read aloud as C D X X I.
Roman numeral converter
Convert a number into Roman numerals, or read a Roman numeral back into a number. Works for 1 to 3999, the range the seven standard symbols can express.
How 421 breaks down into Roman numerals
400 + 20 + 1 = 421, so CD + XX + I = CDXXI.
| Place value | Roman numeral | Why | Copy |
|---|---|---|---|
| 400 | CD | CD is the subtractive form for 400 | |
| 20 | XX | X is 10, written 2 times | |
| 1 | I | I is 1 |
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Numbers either side of 421
- 416 = CDXVI
- 417 = CDXVII
- 418 = CDXVIII
- 419 = CDXIX
- 420 = CDXX
- 422 = CDXXII
- 423 = CDXXIII
- 424 = CDXXIV
- 425 = CDXXV
- 426 = CDXXVI
Related numbers
Browse the full charts: Roman numerals hub, 1 to 100, years 1900 to 2100.
How to write 421 in Roman numerals, step by step
Roman numerals are built from largest value to smallest. Split 421 into place values first: 400 + 20 + 1.
Now swap each part for its symbols: 400 becomes CD, 20 becomes XX, 1 becomes I. Written together that is CDXXI.
The pair CD must stay in that order. CD means "one before 500", so it is read as 400.
- 400 = CD (CD is the subtractive form for 400)
- 20 = XX (X is 10, written 2 times)
- 1 = I (I is 1)
Is CDXXI written correctly?
Yes. CDXXI is the standard modern form of 421. A valid Roman numeral never repeats a symbol more than three times in a row, never repeats V, L or D at all, and only ever subtracts I, X or C, and only from the next two larger symbols.
Those rules are what keeps a number to a single accepted spelling, so a reader never has to guess.
How to type CDXXI on a keyboard
Roman numerals are ordinary capital letters, so you can type CDXXI directly: C, D, X, X, I. Nothing special is required and it will work in any font, any document and any web form.
Unicode also contains dedicated Roman numeral characters such as Ⅰ, Ⅴ, Ⅹ, Ⅼ, Ⅽ, Ⅾ and Ⅿ. They exist for typesetting East Asian text and they look almost identical, but search engines, spell checkers and screen readers handle the plain letters better, so the letters are usually the right choice.
Where you will see CDXXI
Numbers of this size turn up as chapter and page numbers in front matter, as list levels in outlines, as monarch and pope regnal numbers, and in the names of recurring events such as Super Bowl finals.
If you are using CDXXI in a document, keep it in capitals. Lowercase roman numerals (cdxxi) are conventionally reserved for preliminary page numbering and sub-lists.
Frequently asked questions
How do you write 421 in Roman numerals?
421 is written CDXXI. Break it into 400 + 20 + 1, then write CD + XX + I, which joins up as CDXXI.
What number is CDXXI?
CDXXI is 421, or four hundred twenty-one in words.
Is there another way to write 421 in Roman numerals?
Not in standard use. CDXXI is the accepted form because Roman numerals subtract rather than repeat a symbol four times.
How do I copy CDXXI?
Click the large numeral at the top of this page. It copies straight to your clipboard, ready to paste anywhere.
Do Roman numerals have a zero?
No. The system has no symbol for zero and no way to write a negative number or a fraction of one, which is one reason it was replaced for arithmetic.