I have the number thing. Numbers and letters have personality and a visual thing (complete with varying degrees of light). It's light at one, gets dark around 6 or 7, and lightens up around ten, and darkens again.
It's linear, and needless to say it made learning non-linear maths very hard for me. When I was very young, words (not all, but a lot) had visual connections for me that sometimes made sense in context with the word, but sometimes didn't. It lessened over time, and the loss of the word thing might have had something to do with my learning to read.
I never knew what it was, and I felt a bit ashamed of it after telling a few people, and them taking it really as me being a bit strange.
I had an acquaintance growing up who had the word/name taste thing. I never connected it to my number/letter thing. I was considered gifted in everything but maths, and I thought that it was some form of number learning disability growing up. I was pretty ashamed of it.
And it is hard to explain to others. The shading is just the easiest for me to explain. I can't really explain to people why I wouldn't invite 7 to babysit my kids.