420 in Roman numerals
CDXX
The number 420 is written CDXX in Roman numerals.
How CDXX breaks down
| Symbols | Value |
|---|---|
CD | 400 |
XX | 2 × 10 = 20 |
CDXX | 420 |
This numeral uses the subtractive rule: a smaller symbol placed before a larger one is subtracted from it. Only six such pairs are legal — IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
Nearby numbers
| Number | Roman numeral |
|---|---|
| 415 | CDXV |
| 416 | CDXVI |
| 417 | CDXVII |
| 418 | CDXVIII |
| 419 | CDXIX |
| 420 | CDXX |
| 421 | CDXXI |
| 422 | CDXXII |
| 423 | CDXXIII |
| 424 | CDXXIV |
| 425 | CDXXV |
The seven symbols
I | 1 | C | 100 |
V | 5 | D | 500 |
X | 10 | M | 1,000 |
L | 50 |
420 in other notations
| Roman | CDXX |
| Binary | 110100100 |
| Hexadecimal | 1A4 |
| Octal | 644 |
| Written out | four hundred and twenty |
Writing it by hand
Work down through the symbol values, taking as many of each as will fit before moving to the next. For 420:
CD = 400 remaining: 20
2 × X = 20 remaining: 0The result reads CDXX — 4 characters, against 3 digits in Arabic numerals.
Frequently asked questions
What is 420 in Roman numerals?
CDXX
How do you read CDXX?
Work left to right, adding each symbol — except where a smaller symbol precedes a larger one, in which case it is subtracted. CD is 400, XX is 20, giving 420 in total.
How do you write 420 in words?
four hundred and twenty.
Why is there no zero?
Roman numerals have no symbol for zero. The concept reached Europe only with Hindu-Arabic numerals, centuries after the system was in use — which is a large part of why it was eventually replaced for arithmetic.