421 in Roman numerals
421 in Roman numerals
CDXXI
421 is written CDXXI in Roman numerals. That is 4 symbol groups added together, reading left to right from the largest value down.
How it breaks down
| Group | Value | Subtraction | Running total |
|---|---|---|---|
| CD | 400 | D − C | 400 |
| X | 10 | — | 410 |
| X | 10 | — | 420 |
| I | 1 | — | 421 |
Why the smaller symbol comes first
CDXXI uses subtractive notation in one place: CD means D minus C, or 400. A smaller symbol placed before a larger one is subtracted from it rather than added, which is why IX is nine and not eleven.
Only six such pairs are valid — IV, IX, XL, XC, CD and CM. That restriction is what makes the notation unambiguous: IIII and IC both look like they should work, but neither is standard, and only one spelling of any number is correct.
The symbols
| Symbol | Value | Used here |
|---|---|---|
| I | 1 | yes — 1× |
| V | 5 | no |
| X | 10 | yes — 2× |
| L | 50 | no |
| C | 100 | yes — 1× |
| D | 500 | yes — 1× |
| M | 1,000 | no |
The same number, other ways
- In words
- Four hundred twenty-one
- Roman numeral
- CDXXI
- Symbol count
- 5 characters
- Binary
- 110100101
- Hexadecimal
- 1A5
The numbers either side
| Number | Roman numeral |
|---|---|
| 419 | CDXIX |
| 420 | CDXX |
| 421 | CDXXI ← |
| 422 | CDXXII |
| 423 | CDXXIII |
Common questions
- What is 421 in Roman numerals?
- 421 is CDXXI.
- What does CDXXI mean?
- CDXXI is the Roman numeral for 421 — 400 + 10 + 10 + 1.
- How do you write 421 in Roman numerals?
- Take the largest value that fits and repeat until nothing is left: CD (400), then X (10), then X (10), then I (1). That gives CDXXI.
Related pages
- 419 in Roman numerals CDXIX
- 420 in Roman numerals CDXX
- 422 in Roman numerals CDXXII
- 423 in Roman numerals CDXXIII
- 4 in Roman numerals IV
- 9 in Roman numerals IX
- 14 in Roman numerals XIV
- 19 in Roman numerals XIX
- 40 in Roman numerals XL
- 42 in Roman numerals XLII
- 49 in Roman numerals XLIX
- 50 in Roman numerals L
Sources
- Calculated on this page — At One Place