What is the Roman Numeral Symbol for Ten Million ? One Hundred Million ? and so on ....?

Answer 1

For large numbers, the Romans placed a partial frame around numbers (open at the bottom), which indicated that the framed number was to be multiplied by 100000
In more recent practice, the strokes were sometimes written only on the sides, e.g., (Cajori 19993, p. 32).

|X| = 1,000,000
|C) = 10,000,000
|M| = 1,000,000,000
etc

It should also be noted that the Romans themselves never wrote M for 1000, but instead wrote (I) for 1000, (I)(I) for 2000, etc., and also occasionally wrote IM, IIM, etc. However, in the Middle Ages, the use of M became quite common. The Romans sometimes used multiple parentheses to denote nested multiplications by 10, so (I) for 1000, ((I)) for 10000, (((I))) for 100000, etc.

The Romans also occasionally used a vinculum (called a titulus in the Middle Ages), which looks like a horizontal bar, over the top of a Roman numeral to indicate multiplication by 1000.