To save numbers, prefix them with a hyphen, eg #-123
I don’t know any plugin which you could use, so the only way to convert your numbers would be to process your notes in batch through some kind of scripting language.
In your case, Applescript. Check out MacScripter for examples.
The way to process your notes would be:
- Know the path to your notes
- loop through your notes
- Read a note and convert any number with the tag prefix
#- - Rewrite a note.