The numbers 640 to 646 in roman numerals
The right column shows how each roman numeral adds up to the total.
| 640 | = | DCXL | = | 500 + 100 + 50 − 10 |
| 641 | = | DCXLI | = | 500 + 100 + 50 − 10 + 1 |
| 642 | = | DCXLII | = | 500 + 100 + 50 − 10 + 1 + 1 |
| 643 | = | DCXLIII | = | 500 + 100 + 50 − 10 + 1 + 1 + 1 |
| 644 | = | DCXLIV | = | 500 + 100 + 50 − 10 + 5 − 1 |
| 645 | = | DCXLV | = | 500 + 100 + 50 − 10 + 5 |
| 646 | = | DCXLVI | = | 500 + 100 + 50 − 10 + 5 + 1 |