420 in Roman numerals

420 in Roman numerals is CDXX.

Pick any whole number from 1 to 3,999.

420 = \text{CDXX}

How to work it out

1
Take the biggest Roman value that fits, write its letter, subtract it, and repeat.
2
Here: 400 (CD) + 10 (X) + 10 (X) = 420.
3
Joined together: CDXX. (Four of the same letter in a row is never used: 4 is IV, 9 is IX, 40 is XL, 90 is XC, 400 is CD, 900 is CM.)

What is 420 in Roman numerals?

CDXX.

How do you read CDXX?

CDXX = 400 + 10 + 10 = 420.