- An integer is a whole number (not a fractional number) that can be positive, negative, or zero. Examples of integers are: -5, 1, 0, 5, 89, ...
- A positive integer is an integer that is larger than zero. Examples of integers are: 1, 2, 3, 4, 5, ...
- A negative integer is an integer that is less than zero. Examples of integers are: -1, -2, -3, -4, -5, ...
- A whole number is a member of the set of positive integers and zero. Examples of whole numbers are: 0, 1, 2, 3, ...
- A natural number is a member of the set of positive integers. Examples of natural numbers are: 1, 2, 3, ...
- An even number is an integer number divisible by 2. Examples of even numbers are: -2, 0, 2, 4, ...
- An odd number is an integer number not divisible by 2. Examples of odd numbers are: -1, 1, 3, 5, ...
- A prime number(or a prime) is a natural number which has exactly two distinct natural number factors: 1 and itself. Examples of prime numbers are: 2, 3, 5, 7, 11, 13, ...
- A composite number(or a composite) is a natural number which is not a prime, and has a factor other than 1 or itself. Examples of composite numbers are: 4, 6, 8, 9, 10, 12, ...
Below are some of the common useful properties about the operations of even and odd numbers.
- Even ± Even = Even
4 + 2 = 6, 8 − 2 = 6
- Odd ± Odd = Even
3 + 5 = 8, 9 − 3 = 6
- Even ± Odd = Odd, or Odd ± Even = Odd
4 + 5 = 9, 9 − 6 = 3
- Even × Even = Even
2 × 4 = 8, 4 × 6 = 24
- Even × Odd = Even, or Odd × Even = Even
2 × 5 = 10, 3 × 4 = 12
- Odd × Odd = Odd
3 × 5 = 15, 9 × 1 = 9
Below are some of the common useful properties about the operations of positive and negative numbers.
- Positive + Positive = Positive
3 + 5 = 8, 2 + 4 = 6
- Positive − Negative = Positive
1 − (-4) = 5, 3 − (-10) = 13
- Negative + Negative = Negative
(-2) + (-7) = -9
- Negative − Positive = Negative
(-3) − 4 = -7, (-1) − 9 = -10
- Positive × Positive = Positive
1 × 3 = 3, 2 × 5 = 10
- Negative × Negative = Positive
(-3) × (-8) = 24
- Positive × Negative = Negative, or Negative × Positive = Negative
3 × (-2) = -6, (-9) × 2 = -18
Order of operations
- ( )
- × ÷
- + −
(3 + 9) ÷ (1 + 2) = (12) ÷ (3) = 4
1 + 2 × 3 − 4 = 1 + 6 − 4 = 3
3 × 6 ÷ 2 = 18 ÷ 2 = 9