In Plato's Republic, when discussing how the Guardians should organize a breeding program for the citizens, Socrates says:
"Though the rulers you have trained for your city are wise, reason and perception will not always enable them to hit on the right and wrong times for breeding; some time they will miss them, and then children will be begotten amiss."
Fortunately, says Socrates, it can all be worked out by mathematics:
"For the number of the human creature is the first in which root and square multiplications (comprising three dimensions and four limits) of basic numbers which make like and unlike, and which increase and decrease, produce a final result in completely commensurate terms."
This seemingly indecipherable text can be better understood when it is realized that in Plato's day there was no word for "cubed", and that 216 is the first (smallest) cube which is the sum of three cubes. Most scholars agree that the number referred to is 216.
In the Bible, the number of a man is 666. Given that Plato's Republic was written 400 years before the Revelation of St. John, it has been hypothesized that 216 was the originally intended number of a man. Read the original article "The Number of the Beast" here. Indeed, some versions of the Bible have the number as 616, which is a hybrid between the two.
Revelation 666 : "For it is the number of a man..."
Plato 6*6*6 : "For the number of the human creature is…"
Number of The Beast 216 cartoon
Cartoon courtesy of New Scientist. 12 Aug 1989
That 216 is a "human number” can be appreciated when the following facts are considered:
216 days = 7 months (minimum human gestation period)
normal gestation period = 276 days = 33 + 43 + 53 + (3 x 4 x 5)