The number system is extremely old and has been expressed in many ancient cultures for practical uses. Currently the most popular type of number system that is prevalent today is known as the Hindu Arabic numerals. The number system notation development is credited to two great mathematicians from ancient India, Aryabhat (5^{th} century BC) and Brahmagupta (6^{th} century BC). The simplest number system where even number is represented by marks is known as the unary numeral system. Here each and every natural number is represented by the number of corresponding marks, much like the tally marks that are still in use. This system is still used for teaching theories in computer science and can be used in practical use, but for smaller numbers only.

The ancient Egyptians and Romans modified this concept and laid down their own numerical system for various practical purposes. Many others like the Mayan system used the base 20 system. The place value system of numbers that has a base of ten uses 10 digits from 0 – 9 for making the positional numeral system work. This system makes it easier for working in arithmetic rather than other numeral systems. For the purpose of computer science, a modified k positional system is used, which is known as bijective numeration.

India invented the numbers (400CE)

Ummm, actually you gotta figure the egyptians were using mathematics well before the 6th century BC. Its simple logic, they had to have numerical concepts to design and build the pyramids with the level of precision they did, and most of the actual pyramids were built long before the 5th or sixth century bc. Pretty sure the olmecs in mesoamerica had numerical systems before then as well. likewise the celts in northern europe. but yeah the current system of 0-9 as digits and all was greek in origin.