VMS Help FORTRAN, Data, Types, Integer  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Integer values are stored in two's complement form; INTEGER*2 uses
  two contiguous bytes and must be in the range -32768 to 32767.
  INTEGER*4 uses four contiguous bytes and must be in the range
  -2147483648 to 2147483647.  If the value is in the range of an
  INTEGER*2, then the first word can be referenced as an INTEGER*2
  value.