> An Arab mathematician invented it, and it starts at the right because we write numbers that way.
> He was right, you know!
No, he was not. Karl Menninger in Number Words and Number Symbols: A Cultural History of Numbers, p. 530:
The absurdity of this result, of course, at once shows that the numbers themselves, with their decreasing orders of magnitude from left to right must have been incorporated into the Arabic script as foreign borrowings. In the Indian writing, which is read from left to right, the orders of magnitude of the digits also consistently decrease from left to right, but in a right-to-left form of writing like the Arabic alphabet they should also decrease from right to left, as do the ranks of the alphabetical numbers written with the Arabic alphabet.
Babylonian numerals were also written with the least significant "digits" on the right. Uta Merzbach and Carl Boyer in A History of Mathematics p. 24
In a precisely analogous way, the Babylonians made multiple use of such a symbol as II . When they wrote || || ||, clearly separating the three groups of two wedges each, they understood the right-hand group to mean two units, the next group to mean twice their base, 60, and the left-hand group to signify twice the square of their base.
However great the achievements of Arab mathematicians were, our current numeral system was not one of them.
 I replaced the "two wedges" symbol (meaning number 2) with II; I have tried using Unicode codepoint U+12416 which I think should mean just that, but I was never able to convince Gmail to render it correctly in my browser.