Long variables are extended size variables for number storage, and store 32 bits (4 bytes), from -2,147,483,648 to 2,147,483,647.

    long speedOfLight = 186000L;   // see Integer Constants for explanation of the 'L'

  [=long var = val;=]

*var - the long variable name *val - the value assigned to the variable

* byte * int * unsigned int * unsignedlong * Integer Constants * Variable Declaration

Source: arduino.cc