Question about 67 (not a joke)

Not sure if right sub.

My understanding of 67 is that it’s meaningless and that’s the joke. Is there concept for this?

I was thinking that if you were in a group of people and said “69” there would be some smiles and giggles, not because anyone thought of the sexual arrangement, but that 69 has accompanied-the-joke for so long that the mere presence of 69 causes a reaction. It’s become its own joke outside of the sexual arrangement, and seems to me to lack any meaning in the same way.

So like are these a thing? Same thing? Different thing? Wrong sub?

https://redd.it/1wr3rd1
@r_etymology