while not an ENFP, I have bored physics people to death while talking about the history and "interestingness" of math, e.g. von grothendieck's "prime number"
That's probably one of those times where each look at the other person and think to ourselves "OMG, your so amazingly nerdy!"
note: alexander von grothendieck is a very famous dude in the mathematical subject of category theory, whose best brief description that I can try to give is "its like taking abstract algebra [groups, rings, fields, ideals, etc], and abstracting it again [morphisms, functors, etc]". Well category theory is pretty darn abstract, "I will take the category of all groups!", and apparently good ol andy was quite the theorist, as in not practical. one of his number theory buddies apparently found some new computational theorem involving prime numbers and wanted to "show it off" to vG. So he asked vG to pick a random number, to which vG responded "what, an *actual* particular specific prime number???" to which the response was akin to "yes, an actual specific particular prime number, now pick one already" to which VG responded something like "well alright, if I have to pick one, let's go with 51". This is funny because 51 isn't even actually a prime number [3*17=51]. Hence vG's "prime number".