667 - “fax number of the beast” - that was funny ;)
The thing about mathematics is that it can tickle your brain - in a creative way.
It's becoming increasingly difficult these days, with so many things competing for your attention and "brain-deadening" you. It was a wonderful thing to be bored and play around with math. My favorite moments were the epiphany - that there is some hidden connection between math areas or something got new meaning.