When did the Arabic numeral system develop?
Hindu–Arabic numeral system
between the 1st and 4th centuries
It was invented between the 1st and 4th centuries by Indian mathematicians. The system was adopted in Arabic mathematics by the 9th century. Influential were the books of Muḥammad ibn Mūsā al-Khwārizmī[3] (On the Calculation with Hindu Numerals, c.825) and  Al-Kindi (On the Use of the Hindu Numerals, c.830).  The system later spread to medieval Europe by the High Middle Ages.