421 in Roman Numerals
421 in Roman numerals is CDXXI, and is spelled four hundred twenty-one.
How to write 421 in Roman numerals
To write 421 in Roman numerals, combine CD (400), XX (20) and I (1) to get CDXXI.
The numeral CDXXI is read from left to right, from the largest value to the smallest, adding each symbol as you go. It uses subtractive notation — CD — where a smaller symbol placed before a larger one is subtracted rather than added (for example, CD means 500 − 100 = 400).
| Value | Roman |
|---|---|
| 400 | CD |
| 20 | XX |
| 1 | I |
| 421 | CDXXI |
Facts about the number 421
- 421 is an odd number.
- 421 is a prime number: it has no divisors other than 1 and itself.
- The digits of 421 add up to 7.
- 421 has 2 divisors.
421 in other number systems
| Decimal | 421 |
| Roman | CDXXI |
| Binary | 110100101 |
| Octal | 645 |
| Hexadecimal | 1A5 |
Frequently asked questions
How do you write 421 in Roman numerals?
421 is written as CDXXI in Roman numerals.
What does the Roman numeral CDXXI mean?
CDXXI represents the number 421 (four hundred twenty-one).
Is 421 a prime number?
Yes, 421 is a prime number.
What is 421 in binary and hexadecimal?
421 is 110100101 in binary and 1A5 in hexadecimal.
Related numbers
Or open 421 in the converter and browse the full Roman numerals chart.