Such a symbol is called a "variable". It can be a letter, a group of letters (especially in computer programming), or a letter with a subscript (a lowered number, or some other letter - this is more common in math). The letters need not be from the Latin alphabet; Greek letters, or sometimes Hebrew letters, are also used.
Literal numbers are the letters which are used to represent a number.
A letter used to represent numbers is called a variable; the most common ones are 'x' and 'y'.
It used a semi-logarithm representation of numbers.
Numerals are symbols used to represent numbers.
Numbers are used in geometry as natural numbers which are used to represent the dimensions of side, numbers can also be used in the measure of angle which is in degree but can be converted into radians.
The letters of the Greek alphabet, Alpha, Beta, Gamma etc., etc. both upper and lower cases, were used to represent numbers
variable
Variables
0 and 1.
The Morse code
A number is an arithmetic value used to represent quantity.
The letter Q in blackboard bold is used to represent the set of rational numbers - Q standing for quotient.