How many years did the Roman Empire last from the beginning of the reign of Octavian Augustus?

After several centuries of republican rule in Rome, a power struggle began among powerful politicians. At first it was just tyranny, and formally the Senate had tremendous power (under Julius Caesar). However, Octavian Augustus in 27 BC. established his power as emperor. After that, until the collapse of the country into two parts in 395, the Roman Empire existed. And so it turns out that the empire lasted 422 years.