Do you know any formal synonym words/expressions of "being good with numbers"?
I can think of expressions such as "numerical literacy", but they do not mean exactly the same.
Thank you.
If you mean the direct complement to literacy, it is numeracy
It does not convey a sense of 'great skill' but basic, essential comprehension of the concepts involved.
After comments
As far as I'm aware, there is no distinct word between 'numeracy' & 'mathematician'. There are only comparatives - basic, skilled, low, high, etc.
Just use an adverb:
Highly numerate.
There is a distinction between being highly numerate, and being good at mathematics. Many mathematicians are good at solving maths problems, but don't do complex calculations much.
John worked as an accountant from 1943 to 1975. He didn't have a calculator or computer, so he was highly numerate.
If you were describing a person, you might say that they were mathematically inclined, which would mean they have a natural talent or interest in mathematics. The noun form would be "mathematical inclination," but that is much less commonly used.
"Numerate" means having the ability to understand and work with numbers.
The opposite of this is innumerate, meaning the inability in the same area. This is comparable with literate and illiterate, which mean respectively that you can, or cannot read.
Note though, that 'numerate' merely means you have the ability, not that you are especially gifted. You could reason that most people are literate, meaning they can read, but they may not read to the standard of a professional newsreader, for example.
The word 'superliterate', meaning exceptionally literate, appears in some dictionaries, although not the most scholarly ones I normally rely on. However, I can see the word, along with 'superliteracy' used in what I would consider scholarly documents on the website of the Modern Language Association, as well as in various publications. Logically, someone who is exceptionally numerate could be supernumerate.