From the list of Roman emperors below, who reigned the longest?

The information about the reign of the emperors from the list:

• Augustus: 40 years, 7 months and 3 days.
• Antonius Pius: 22 years, 6 months and 28 days
• Tiberius: 22 years, 5 months and 27 days
• Hadrianus: 20 years, 10 months and 30 days

Augustus, the first emperor of the Roman Empire, was careful to maintain the face of republican rule, taking no specific title for his position. He had an extraordinary talent for constructive statesmanship and sought to preserve the best traditions of republican Rome. The reign of the first Emperor of one of the most powerful empires of all time set the direction for the development of Rome in the course of another 3 centuries.