A number is a theoretical concept, and a numeral is the way that people denote that concept. A numeral contains one or more written symbols, but a number can be expressed in a range of ways. Number and numeral are often used interchangeably, but there is a slight difference between them.
For instance, the number 5 is a concept used to describe five objects. One could express this concept by holding up five fingers or by saying the word "five." However, if one wrote down the number "5" that would be a numeral. Regardless of whether the person wrote that number using Roman (V) or Arabic (5) numerals or even letters (five), it would still be considered a numeral once it was written. \
Any written number can be a numeral, regardless of how many symbols or digits it takes to create that number. For instance, "5" is a numeral but so is "505" and "5,678,987." However, the word numeral can not be used interchangeably with digit. A digit is a single symbol used to make a number or numeral. The number 5 can be written with just one symbol or digit, while the number 505 needs three digits and 5,678,987 needs seven digits.