I heard from one of my teachers in school that the number 666 is actually the wrong number/date that relates to the devil. She did not say what the actual number/date is. Has anyone else heard this??

I've heard of the idea but I'm not sure on all the details. I think there are a couple of ideas from the number being 616 or even 665.

Then again this is also kind of interesting:

link

I heard a story from my friend saying the world will end this June 6 2006. Thats 6/6/06. And i overheard that in class but did not saying anything. But I said to myself that aint true the world won't end this June just because this year is 2006. And plus theres a 0 before the 6. Its funny how ppl try to incorporate the number 666 in many ways in their life. Although I did see my friend's reciept. Whats special about this reciept is that the total money spent on some tacos at Del Taco came out to be $6.66 (This included tax to). LMAO. I guess this is just a coincedence and now hes going to keep it as a soveniere.

I read something once that suggested the number should actually be 6002020206 or rather (600) 202-0206. This is because in the bible it is mentioned as six hundred (600), three score (20, 20, 20) and six (6). Nowhere does it say these should be added so why not list them in a row? Incidentally this is a number in Canada.

The teacher probably meant 616 since that is thought to be in the earlier texts of the New Testament, which by the way, is not the devil's number. It's a human number which some believed was Nero's.

(C&P)
While most manuscripts of the Bible read six-hundred-sixty-six or 666 for the Number of the Beast in Revelation 13:18, some early manuscripts contain 616 instead. Codex Ephraemi Rescriptus (5th century) and Papyrus 115 (3rd or 4th century). Irenaeus knew about the reading 616, but according to Metzger, Bruce M. (1971). A Textual Commentary on the Greek New Testament, New York: United Bible Societies. ISBN 3-438-06010-8., p. 751, Irenaeus "says that 666 'is found in all good and ancient copies,' and is 'attested by those who had themselves seen John face to face.'" The minuscule manuscript 2344 (11th century) identifies the Number of the Beast as 665.

In May 2005 it was reported that scholars at Oxford University using advanced imaging techniques had been able to read previously illegible portions of an early (third century) version of the Book of Revelation, part of its Oxyrhynchus collection of papyri. The fragment gives the Number of the Beast as 616.