Where was the number system invented?

Answer
The numeral system or decimal system is of Hindu-Arabic origin.

Aryabhatta and Brahmagupta had developed decimal number system and four fundamental operations.

The real impact of Brahmagupta's discoveries was felt in the Islamic world, where King Khalif Abbasid al-Mansoor (712 - 775) invited the Ujjain scholar Kanka to lecture on Brahmagupta's applications of mathematics to astronomy. The king ordered Brahmagupta's writings translated into Arabic in 771, and they had a major impact on subsequent writers in the Arab world, including al-Khwarizmi, the "father of algebra."

The mathematical thought of medieval and early modern Europe was influenced by this Arabic models