The decimal system was invented by the Gupta empire.
The Gupta empire (375-550AD) was an ancient Indian empire situated mainly in the north and central India. It was outstanding not only for mathematics' discoveries but also for important developments made in medicine, astronomy, and art
One of its accomplishments in mathematics, was the discovery of the decimal system and zero as a placeholder, based on the number 10 (similar to what we use nowadays). it was discovered by a mathematician and astronomer named Aryabhatta around 498 CE. The system allowed for a more scalable and flexible counting system, new equations, theorems, notations, etc.