https://math.stackexchange.com/questions/1232463/how-to-prove-the-language-of-all-binary-numbers-that-are-prime-is-nonregular-usi https://math.stackexchange.com

https://math.stackexchange.com/questions/1232463/how-to-prove-the-language-of-all-binary-numbers-that-are-prime-is-nonregular-usi https://math.stackexchange.com/questions/1232463/how-to-prov... has a proof for base 2. This method works for other bases too.