I'm pretty sure the poster above you is referring to the differences between the number of letters in the following words: "CLEOPATRA" is closer to "MOON LANDING" than "THE BUILDING OF THE PYRAMIDS".
What people usually refer to the Roman Empire is the unified empire which was only around for 4 centuries.
Heck pretty much past 286 AD is when the Roman Empire is no longer the classical Roman Empire. (Rome was no longer the capital, eastern / western split begins).
Even a bit earlier if you want to consider the shift to the monotheism (not yet Christianity) of Sol as the line of demarcation.
If you want to be utterly pedantic then yes the Eastern Roman Empire survived until 1453 aka the Fall of Constantinople.
So more like 1500 years in total.
