Number « PL SQL Data Types « Oracle PL/SQL Tutorial

21.14.2.NUMBER Subtypes
21.14.3.Identical declarations using NUMBER subtypes.
21.14.4.Number type variable
21.14.5.Assign value to NUMBER type variable
21.14.6.NATURAL value Computation
21.14.7.Assigning a Fraction to an Integer
21.14.8.Setting Precision and Scale
21.14.9.NUMBER(1,-2): Variable with a scale of -2 can only hold values like 100,200,300... up to 900.

21.14.10.NUMBER Data type: integer, fixed point and floating point
21.14.11.Select a number value from a table into a variable and output it
21.14.12.IF statement with number value check