Obvious trolling aside, the whole debate on whether or not 1 is a prime is pretty interesting.

https://en.m.wikipedia.org/wiki/Prim...imality_of_one

If you want to understand why 1 isn't considered a prime number, you can easily look into it.
The TL;DR is that 1 breaks the fundamental theorem of arithmetic and 1 would specifically have to be excluded. Mathematicians have debated 1 as a prime for centuries, came to the conclusion it is not, and 1 is more or less considered the foundation to counting instead.