Over a whole number it was to ensure that it was understood as a number and not a word (also often underlined as well so the number appears between two lines);
Otherwise multiply it by 1000, for example:
_
V = 5 x 1,000 = 5,000
When there is a straight line (known as a vinculum) over a Roman numeral, it typically signifies multiplication. It indicates that the value of that Roman numeral should be multiplied by the number below the vinculum.
It indicates multiplication by a thousand
A bar or a line over a particular Roman numeral indicates that it is to be multiplied by a thousand.
This is not a valid roman numeral!
It is: 5 = V as a Roman numeral
The Roman numeral of DXIII is equivalent to 513
It indicates multiplication by a thousand
In todays modern usage of Roman numerals it indicates multiplication by a thousand.
A bar or a line over a particular Roman numeral indicates that it is to be multiplied by a thousand.
It is: 5 = V as a Roman numeral
This is not a valid roman numeral!
LXXVI is the Roman numeral for 76.
The Roman numeral of DXIII is equivalent to 513
You mean Roman Numeral? It is XVI
It is the Roman Numeral for the number 6. It is the Roman Numeral for the number 6.
The Roman numeral CCLXVI represents the number 266
The Roman numeral CXXXVI represents the number 136
The Roman numeral MMDCXLI represents the number 2641