@JonathanHoefler Thanks for indulging me with your expertise! I think I agree with most of that.
I'd consider √ more like punctuation than a letter of the alphabet.
I didn't really start with the "what's in the alphabet" question -
@JonathanHoefler ... it was more: when writing my salary, I use the 'digitary' 012345678798. When writing a binary number, I use the 'digitary' 01.
It's not about what they mean, it's about which digits can come up.