I've always learned that the difference between 'number' and 'numeral' was that number is the idea and numeral is the representation. But after a discussion with @terdon in chat, I'm not so sure anymore. Different sources say different things.
Like, Merriam Webster defines numeral as:
a conventional symbol that represents a number
But lists 'number' as a synonym.
And in their number entry:
a word, symbol, letter, or combination of symbols representing a number (definition 4)
The top Google result says:
A numeral is a symbol or name that stands for a number. Examples: 3, 49 and twelve are all numerals. So the number is an idea, the numeral is how we write it.
So what is the difference between 'number' and 'numeral'?