Number
840 in Roman numerals
840 is written DCCCXL
Type any other number or numeral below to convert it.
Above 3,999? Type the barred part in brackets, e.g. (IV)CC = 4,200.
How DCCCXL is built
Roman numerals are written one decimal place at a time, largest first.
- DCCChundreds · 8D (500) plus CCC (300) makes 800.
- XLtens · 4X before L means 50 − 10 = 40. This saves writing XXXX.
800 + 40 = 840
The pair XL uses subtraction: a smaller letter before a larger one is taken away from it. Only six pairs work this way: IV, IX, XL, XC, CD and CM. More on subtraction
Mistakes to avoid
- Not DCCCXXXX (8 letters). That adds everything up without subtraction. The Romans sometimes wrote numbers this way, and clocks still show 4 as IIII, but today DCCCXL (6 letters) is the standard.
- There's no letter for zero. The zero is simply left out, which is why 840 has 2 parts, not 3.
About the number 840
- 840 is even and can be split into prime factors: 2 × 2 × 2 × 3 × 5 × 7, or in Roman numerals II × II × II × III × V × VII.
- DCCCXL has 6 letters. 396 of the numbers up to 1,000 have longer numerals.
Counting from 831 to 840
Every number from 831 to 840 starts DCCCX (810); only the ending changes.
| Number | Roman numeral |
|---|---|
| 831 | DCCCXXXI |
| 832 | DCCCXXXII |
| 833 | DCCCXXXIII |
| 834 | DCCCXXXIV |
| 835 | DCCCXXXV |
| 836 | DCCCXXXVI |
| 837 | DCCCXXXVII |
| 838 | DCCCXXXVIII |
| 839 | DCCCXXXIX |
| 840 | DCCCXL |