Numbers Basics

Types of numbers :
1. Natural numbers (N) = 1, 2, 3, . . . .
2. Whole numbers (W) = 0, 1, 2, 3, . . . .
3. Intezers (Z) = −∞ . . . −2, −1, 0, 1, 2, 3, . . .
4. Rational numbers (Q) = The numbers of the form ^p⁄_q  where q ≠ 0.  Eg: ¹⁄₅ , 0.46, 0.333333
5. Irrational numbers (I) = The numbers of the form x^1⁄_n  ≠ Intezer.  Also π and e also irrational numbers.

Other types of numbers:
a. Even numbers : Numbers which are exactly divisible by 2.  These numbers are in the format of 2n.
b. Odd numbers: Numbers which gives remainder 1 when divided by 2. These numbers are in the format of 2n ± 1.
c. Prime numbers : The numbers which are divisible by 1 and the number itself are primes.  The least prime is 2.
d. Composite numbers : The numbers of which are divisible by more than 2 numbers.

The following rules related to Even and Odd numbers are important:
odd ± odd = even;
even ± even = even;
even ± odd = odd

odd × odd = odd;
even × even = even;
even × odd = even.

odd^{(any number)} = odd
even^{(any number)} = even

Fundamental Theorem of Arithmetic: Any intezer greater than 1 is either prime or product of primes. Writing a number as a product of primes is called prime factorization. For example, 100 can be written as 2² × 5²