In Tolkien's legendarium, Fëanor (eldest son of Finwë, the High King of the Noldor) invented the Tengwar script which was used to write the Elven languages Valarin, Quenya (High-elven), Telerin (also called Lindalambë) and Sindarin (Grey-elven). It was also used to write Black Speech, the official language of Mordor, as can be seen in the inscription on the One Ring, forged by Sauron, and familiar to most of us from The Lord of the Rings movie series. As for the numbers, the Elves and the Dwarves used a duodecimal system (base-12), although the Eldar were also known to have used a decimal system too but indicated a preference for the duodecimal system counting in sixes and twelves. In the Third Age, the Men of the West used a decimal system. The numerals in Tengwar were assigned as follows:
0 (ð), 1 (ñ), 2 (ò), 3 (ó), 4 (ô), 5 (õ), 6 (ö), 7 (÷), 8 (ø), 9 (ù), 10 (ú), 11 (û)
The numbers were written ‘backwards’ starting with the least significant digit (unit) first from the left. So if I were to write 1234 in Tengwar, it would be ôóòñ.