Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six. -Rev 13:18
Chris White did a podcast on this, so I will be borrowing heavily from him. Walid Shoebat is the main purveyor of this theory and he uses a lot of alternate definitions and manipulations to make his theory work. Rev 13:18 specifically says to count or calculate the number of the beast, which implies to look at it as a number and not a name.
Count (psēphizō) g5585
I to count with pebbles, to compute, calculate, reckon
II to give one's vote by casting a pebble into the urn
III to decide by voting
Shoebat claims "count" or "calculate" can just as easily mean "reckon" or "decide" and not a number. However, according to all lexicons "reckon" is only used in context of relating to counting or calculating numbers. He then defines "number" (arithmos) as a group of people or "a multitude":
Number (Arithmos) g706
I a fixed and definite number
II an indefinite number, a multitude
Here again "a multitude" is in context of a number, not a group of people. The Bible uses the word "ochlos" (g3793) when describing a crowd of people, not "arithmos". Arithmos is where we get the word arithmetic from, which is another clue its talking about a number and not a multitude of people. If there are any doubts, Greek writers drew lines over letters to indicate that it was part of a number.
So Shoebat wants us to believe that 666 has nothing to do with a number, but the actual definitions do not support this. Shoebat claims at least one translation of the Bible has translated this verse in a similar way, called the "Restoration Scriptures True Name Edition". However, as it turns out this self-published Bible was written by a guy named Koniuchowsky who Walid once knew and collaborated with, so this doesn't lend him much credibility.
So the main claim is Xi Chi Stigma (χξς), 666, on the right looks like the Arabic word for Allah on the left:
At first glance, the combination of Chi and Stigma does somewhat resembles the Arabic word for Allah. One problem is Xi is not represented at all in the Arabic writing. To explain this away, Shoebat wants us to believe the Xi symbol is actually two swords drawn together representing the universal symbol for Islam. Except crossed swords are not the universal symbol for Islam. According to Wikipedia, "The symbols of Islam include calligraphy of important concepts or phrases, such as the shahada, takbir, basmala, etc.; besides this the colour green is often used as symbolising Islam, as is the star and crescent symbol." https://en.wikipedia.org/wiki/Symbols_of_Islam
Walid relies heavily upon the Codex Vaticanus (350 A.D.) at Bob Jones University to support his claim. The problem is the Codex Vaticanus ends at Hebews 9:14 and never included The Book of Revelation. The missing portions were supplemented from a document written in the 15th century (the minuscule Codex 1957). This was written in a specific type of Greek writing called Greek minuscule. If we look at this a 3rd century papyrus we see Xi Chi Stigma looks nothing like the Arabic for Allah:

In some versions it was written as 616, which bares even less of a resemblance:

https://polination.wordpress.com/2014/0 ... the-beast/
So Xi Chi Stigma was not always written the same way. This is the most damaging evidence against Shoebat's theory. This is why he relies so heavily on the Codex Vaticanus to support his theory. Even then to make it work, he has to flip the Arabic word for "Allah" on its side and invert it to even remotely resemble the Greek symbols. The picture on the right is the actual name of Allah, the middle picture is the rotated and inverted edited version which Shoebat uses:

So Shoebat does a lot of manipulating to make his theory fit. If you want to listen to the full podcast go here http://bibleprophecytalk.com/uploads/2b ... own_01.mp3