Even if you aren’t into heavy metal, you probably know that “666” is a number associated with evil. How come? The devil is in the details. Here is a history of 666.

The Book of Revelation was written in Greek sometime between 70 and 95 A.D., by an author known only as John. While its most commonly associated with scary, cryptic, or apocolyptic imagery, it’s really only the 13^th chapter of Revelation where that’s present. It begins with a letter to the reader, then describes cataclysmic events of the end times John says he saw in a series of visions.

It’s in Revelation (13:8) where “666” is mentioned—the only time in the Bible: “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.” Doing a bit of quick math, in which a score is 20, the number adds up to 666. Whoever is represented by this number then, the text indicates, is pure evil.

Specifically, the beast referenced here is the beast from the sea, the first of two beasts previously described in Revelation. The beast from the sea is described as having “seven heads, ten horns,” and a leopard-like form with the “feet of a bear” and the “mouth of a lion.” The second beast, also referred to as the false prophet, comes out of the earth and directs people to worship the first beast.

Although most English translations of the Bible give the number of the beast as 666, there’s been disagreement for centuries over whether the number is really…616. One key piece of evidence: an ancient scrap of paper called “Papyrus 115,” a fragment of a manuscript of the New Testament, including parts of Revelation, dating to about 225 A.D. It was found in Egypt by Oxford archaeologists in the early 20th century and clearly gives the number as 616.

Throughout history, people have tried to identify whom Revelation could be referring to as the “beast of the sea” by using the number. They do so by using Koine Greek or Ancient Hebrew alphabets, as numbers in those languages were represented by letters, which made it easy to translate any name into a number (and those are also languages the Bible was written in).

Some scholars think that that alphanumeric code points to one, or at the least the first “beast” of Revelation: Nero. Unfortunately, even using Nero’s name can’t give insight into whether the number of the beast is 616 or 666, as the Greek version of the name and title transliterated into Hebrew gives the number as 666, while the Latin version of the name translates into Hebrew and yields the number 616.