Important of Number 4

1                                                   Important Characteristics of Number 4    

It is a square number, i.e 2² = 4                      

2.      The word FOUR has four letters. In the English language there is no other number whose number of letters is equal to its value.                                                                            

        FOUR = 4 (Number of Letters)

3.      A tetrahedron has four triangular faces.         

                                  

4.      In DNA molecules Thymine (T), Adenosine (A), Guanine (G) and Cytosine (C) are the four bases

5.      Four dimensional has four dimensions namely- Length, Breadth, Height and Time. It is denoted by (x, y, z, t).

6.      There are four fundamental operations in math. They are – Addition (+), subtraction (− ) , Multiplication (x ) and Division (÷).

7.      It is the smallest number of colours sufficient to colour all planar maps with no adjoining countries showing the same colour.

8.      4 is the smallest composite that is equal to the sum of its prime, i.e. 4 = 2 + 2

9.      4 is the smallest squared prime ( p² ) and the only even in the form 4 = 2².

10.  Lagrange’s four square theorem states that every composite integer can be written as the sum of at most four square numbers.   This theorem was proved in 1770.                                   

                   Example :         3 = 1² + 1² + 1² + 0²

31 = 5² + 2² + 1² + 1²

310 = 17² + 4² + 2² + 1².

11.  In human there are four blood groups namely A, B, AB and O.

12.  Humans have four canines, four incisors and four wisdom teeth.

13.  Atomic number of Beryllium is 4 and valency of Carbon is also four.

14.  A 4 x 4 square has an area equal to its perimeter.

            Perimeter = 4 + 4 + 4 + 4 = 16 unit                                                                                                           Area = 4 x 4 = 16 square unit

15.  x² – y² is divisible by 4 only when x – y is even.

16.  Any prime of the form 4k + 1 is the sum of two square numbers.          

                               13 = 4 x 3 + 1 = 2² + 3²                                                 

                               73 = 4 x 18 + 1 = 3² + 8²

17.  It can be portioned in 5 ways.

18.  4 is the smallest honest number. Numbers n that can be described using exactly n letters in standard mathematical English. Four has 4 letters. It is the smallest honest number.

19.  4 is the smallest composite number. A number is said to be composite if it has more than 2 factors. 4 has the factors 1, 2 and 4.

20.  A number is divisible by 4 if it last two digits is either 00 or divisible by 4. Example: - 100, 1465784 is divisible by 4.

21.  There are four suits in playing cards. They are – Clubs, Diamonds, Spade and Heart.

22. 4² = 2⁴ is the solution of the equation    a^b =b^a

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Rajesh Kumar Thakur

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