The number system what we use today (1,2,3,4,5…) is called ARABIC NUMBERS SYSTEM. We also have Roman Numbers System (I, II, III, IV, V, …) which is rarely being used.
Have you ever thought Why One is 1, Two is 2, Three is 3 … and so on? It is all because of Angles. Yes, it is the number of angles in each letter.