• What are numbers ?
  • Number are just idea is mind, they are just labels for naming and recording the size of collection of objects.
  • For 4 objects, we could also hold up 4 fingers, or tap the ground 4 times, it just idea of telling people what you have in mind.
  • If you draw something like ‘5’ and people understand your mean about 5 objects’, good go ahead and use them. If they don’t understand that, try ‘V’ they might be understand, probably you are with ROMANs.
  • Or some character in chinese, so the base idea is number just are ideas of our mind, or the way we have trained our mind to see and understand objects, how to tell it other people is completely left to us. It can be in roman numeral, or simply by counting fingers or any form like https://en.wikipedia.org/wiki/%C4%80ryabha%E1%B9%ADa_numeration.
• What are numerals ?
  • Numerals like 1, 2, 39 .. are just representation of numbers, that normally now people use to understand counts of objects(numbers)
• What is digits ?
  • A digit is a single symbol used to make numerals
  • 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 are the ten digits we use in everyday numerals in modern(so-called(‘modern’ IMO is most abused word) system.
  • Example: The numeral 153 is made up of 3 digits (“1”, “5” and “3”).

If you have any familarity with computers format like unicode. Below defination is very apt

“Numbers are like unicode code points and numerals are like UTF-8/UTF-16 encoding, unicode is label for alphabet or characters we know, and how to write it goes into the way we do encoding for it.”