A 64 bit sized integer - the largest in Delphi System unit
  type Int64 = -9223372036854775808..9223372036854775807;
The Int64 type is a 64 bit signed Integer. This size is fixed, and will not change in future releases of Delphi.
Functions such as IntToStr support Int64 (via overloading).
Integer constants are cast to Int64 type when they exceed Integer size.
There is no unsigned 64 bit integer type in Delphi.
Related commands
Byte An integer type supporting values 0 to 255
Cardinal The basic unsigned integer type
Integer The basic Integer type
LongInt An Integer whose size is guaranteed to be 32 bits
LongWord A 32 bit unsigned integer
PInt64 Pointer to an Int64 value
ShortInt An integer type supporting values -128 to 127
SmallInt An Integer type supporting values from -32768 to 32767
Word An integer type supporting values 0 to 65535
Example code : Showing the capacity of Int64
  min, max : Int64;
  // Set the minimum and maximum values of this data type
  min := Low(Int64);
  max := High(Int64);
  ShowMessage('Min int64 value = '+IntToStr(min));
  ShowMessage('Max int64 value = '+IntToStr(max));
Show full unit code
   Min int64 value = -9223372036854775808
   Max int64 value = 9223372036854775807