The church father Irenaeus (130-202) said there were many names that could be produced from the number, and he speculates about the name using the “Greek fashion of calculation”, using the value of the letters contained in 666 and trying to mathematically produce a name. He attributes the erroneous number 616 to a copyist error, and states that none of the names produced is certain. This would indicate that it wasn’t anything that he learned from the apostolic teaching tradition. However, Irenaeus offered an alternative interpretation of 666.
And he will cause a mark [to be put] in the forehead and in the right hand, that no one may be able to buy or sell, unless he who has the mark of the name of the beast or the number of his name; and the number is six hundred and sixty-six,” (Rev 13:18) that is, six times a hundred, six times ten, and six units. [He gives this] as a summing up of the whole of that apostasy which has taken place during six thousand years." Irenaeus V.XXVIII.2
For in as many days as this world was made, in so many thousand years shall it be concluded. And for this reason the Scripture says: “Thus the heaven and the earth were finished, and all their adornment. And God brought to a conclusion upon the sixth day the works that He had made; and God rested upon the seventh day from all His works.” This is an account of the things formerly created, as also it is a prophecy of what is to come. For the day of the Lord is as a thousand years;(2 Pet 3:8) and in six days created things were completed: it is evident, therefore, that they will come to an end at the sixth thousand year. Thus, then, the six hundred years of Noah (Gen 7:6), in whose time the deluge occurred because of the apostasy, and the number of the cubits of the image for which these just men were sent into the fiery furnace (Dan 3:1), do indicate the number of the name of that man in whom is concentrated the whole apostasy of six thousand years, and unrighteousness, and wickedness, and false prophecy, and deception; for which things’ sake a cataclysm of fire shall also come [upon the earth]." V.XXVIII.3
The church father Irenaeus associated the number of the beast (Rev 13:18) with the six days of creation as well as 6,000 years of Earth history. Irenaeus was a disciple of Polycarp who was a disciple of John. Of course, Irenaeus got the number from the book of Revelation. According to this church father, the number was foreshadowed by the six days of creation, the flood, and the book of Daniel.
Surprisingly, the idea for 666 was preceded by the first-century Jewish scholar Philo of Alexandria (25 BC-50 AD).
Since, therefore, the first beginning of the generation of our race, after the destruction caused by the deluge, commenced with Noah, men being again sown and procreated, therefore he also is recognised as resembling the first man born of the earth, as far as such resemblance or recognition is possible. And the six hundredth year has for its origin the number six; and the world was created under the number six, therefore, by this same number does he reprove the wicked, putting them to shame because he would, unquestionably, never, after he had created the universe by means of the number six, have destroyed all the men who lived on the earth under the form of six, if it had not been for the preposterous excess of their iniquities. For the third power of six and the minor power is the number six hundred, and the mean between both is sixty, since the number ten more evidently represents the likeness of unity, and the number a hundred represents the minor power." Philo, Book 42: Questions and Answers on Genesis, II
Here is a quote from Hippolytus of Rome (170-235).
- But that we may not leave our subject at this point undemonstrated, we are obliged to discuss the matter of the times, of which a man should not speak hastily, because they are a light to him. For as the times are noted from the foundation of the world, and reckoned from Adam, they set clearly before us the matter with which our inquiry deals. For the first appearance of our Lord in the flesh took place in Bethlehem, under Augustus, in the year 5500; and He suffered in the thirty-third year. And 6,000 years must needs be accomplished, in order that the Sabbath may come, the rest, the holy day “on which God rested from all His works.” (Heb 4:4) For the Sabbath is the type and emblem of the future kingdom of the saints, when they “shall reign with Christ,” (Heb 4:5, Rev 20:6) when He comes from heaven, as John says in his Apocalypse: for “a day with the Lord is as a thousand years.” (2 Pet 3:8, Psa 90:4) Since, then, in six days God made all things, it follows that 6,000 years must be fulfilled. And they are not yet fulfilled, as John says: “five are fallen; one is,” that is, the sixth; “the other is not yet come.” (Rev 17:10) The interpretation by Hippolytus, Daniel