Having actually done a little number theoretical stuff back in the day, I see what you mean, but prosaically this was astonishing enough for me to make the link

Having actually done a little number theoretical stuff back in the day, I see what you mean, but prosaically this was astonishing enough for me to make the link worth posting: Decimal characters include digit characters, and all characters that can be used to form decimal-radix numbers, e.g. U+0660, ARABIC-INDIC DIGIT ZERO. Rigid designators vs definite descriptions for numerals, anyone?