A long integer is a data type in computer science whose range is greater (sometimes even double) than that of the standard data type integer. Depending on the programming language and the computer machine processor, the size of the long integer will vary. In some programming languages, the size of the long integer is standard and fixed across different platforms, while in others, it depends on the processor. There are certain programming languages that do not make use of long integers, but they are used in many programming languages for holding a long range of values, especially during mathematical computations.
Techopedia explains Long Integer
Like a standard type integer, long integers are represented as a set of binary digits. Long integers can be unsigned (representation of non-negative integers) or signed (representation of negative integers). Most programming language have defined the minimum and maximum value of the integers that can be represented by long integers.
The size of long integers in different programming languages is as followers: