The Parthian Empire, which had been a terrible nightmare for Rome, was eventually defeated by an internal enemy: the Sassanid Persians, led by Ardacher I. This empire, which existed between 224 and 651 AD, controlled a vast territory that encompassed present-day Iran, Iraq, Azerbaijan, Armenia, Afghanistan, parts of Turkey and Syria, as well as extensions into Pakistan, Central Asia, and Arabia. At its height, during the reign of Choroes II, it rivaled both the Roman and Byzantine Empires.

Although unjustly forgotten, it was a key empire in the ancient history of the Middle East, due to its military, administrative (centralized unlike the Parthians), and cultural power, as well as its advances in science such as medicine. Their religion was Zoroastrianism, of which they were fervent defenders.

Their monetary system was based on the silver drachma , a coin with a large diameter (approximately 30 mm) but very thin.

They also minted other coins, such as the hemidrachma (half a drachma), the obolus (one-sixth of a drachma), and the tetradrachma (four drachmas). They also minted other coins in copper, fleece, and even gold; the dinar. Their designs influenced numerous subsequent cultures.

Islam ended the Sassanid Empire in 651 AD.

Here you can see our KING LIST OF THE SASSANID PERSIAN EMPIRE.
How many do you think there were?