The Roman number DX corresponds to the arabic number 510.
There is no common alternative notation for this number.
You are looking for acronyms beginning with DX? Here is our list with acronyms starting with DX.
Interesting Fact: In the French Republican Calendar, initiated during the French Revolution, years were numbered by Roman numerals – from the year I (1792) when this calendar was introduced to the year XIV (1805) when it was abandoned.