I think your friend's avoidances are nothing more than unfounded superstition.

In biblical numerology, six is the number of humankind and man's world. Humans were created on the 6th day. According to the 10 commandments, we are supposed to work for 6 days a week. Therefore, some see the number 6 also as a number of sorrow.

There is no notion in the Bible that 6 symbolizes Satan or evil.

As far as 666 (Rev. 13.18) , there are as many guesses as to what it means as there are people guessing. Some of the ideas:

1. Man (6) pretending to be God (three 6s)
2. a 3-fold failure to reach perfection (7)
3. The sum of the letters of "Beast" in Hebrew.
4. The Hebrew letters for "Nero Caesar"
5. A cryptogram of "Nimrod"
6. A triangular number referring to the antichrist.

I don't see any particular biblical reason to avoid the number 6 in the rhythms of our lives.

so i got a friend who always try to avoid the number 6 (for example he prefer to do 70 push ups rather than 60, when we watch a film i put the sound on 16, 26 36 or 60% his changing it to something without a 6...) his telling me that the number symbolize Satan and i should avoid it too.

i know numbers are something "important" in the bible but i only read the "easy to understand" version of bible, Satan showed up only twice there: To Eve and to Jesus, so i got no idea what and why 6 symbolize the Evil (to be fair i only know the meaning of number 3 *correct me if im wrong* : god, son and holy spirit)

so... is it something to avoid or its cool (as soon as its not 666 i guess...)