Arithmetic/Types of Numbers/Integer Number

An integer number is any of: a positive whole number (a positive integer), a negative whole number (a negative integer), or zero.

Positive Integer
A Positive Integer is a natural number greater than 0, i.e. a whole number. A Positive Integer can be expressed mathematically:
 * I > 0 = {+1,+2,+3,+4,+5,+6,+7,+8,+9,...}

Positive numbers are often written without a + sign:


 * I > 0 = {1,2,3,4,5,6,7,8,9,...}

Negative Integer
A Negative Integer is a negative whole number. This is represented by a - sign on the left side of the value.
 * I < 0 = {-1,-2,-3,-4,-5,-6,-7,-8,-9,...}

Number Zero
The Integers include a new number, 0.

Rules

 * 1) a + 0 = a
 * 2) a - 0 = a
 * 3) a × 0 = 0
 * 4) a / 0 is not defined.
 * 5) a + a = 2a
 * 6) a - a = 0
 * 7) a × a = a2
 * 8) a / a = 1 (except for a = 0, which is not defined, see rule 4)
 * 9) a - (-a) = 2a
 * 10) a × (-a) = - a2
 * 11) a / (-a) = -1 (except for a = 0, which is not defined, see rule 4)