Set of natural numbers.
The capital Latin letter N is used in mathematics to represent the set of natural numbers. Usually, the letter is presented with a "double-struck" typeface to indicate that it is the set of natural numbers. Otherwise, N is also used as a variable.
Set of integers symbol.
The set of rational numbers is denoted with the Latin Capital letter Q presented in a double-struck type face.
The set of real numbers symbol is a Latin capital R presented in double-struck typeface.
The set of complex numbers is represented by the Latin capital letter C. The symbol is often presented with a double-struck font face just as with other number sets. The set of complex numbers extends the real numbers.
The set of natural numbers, also called the counting numbers, contains the numbers 0, 1, 2, 3, ...