Factors and Multiples - 2

Prime and composite numbers

As discussed in the last post, there are numbers which have only 2 factors (1 and the number itself). So, I am sure you have figured out the name. 

Yes, indeed! It is called as a Prime number. Therefore, the numbers like 2, 3, 5, 7, 11, 13,... etc are the prime numbers.

In the previous post, we found the factors for the numbers like 6 and 15. They had more than 2 factors. Such numbers are called as Composite numbers. 

In the table below, numbers from 1 to 100 are listed. It provides you an information about each number if it is prime or composite.

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95	96	97	98	99	100

	Unique number
	Prime number
	Composite number

Let's make some observations from the table above.

• The box containing the number '1" is coloured differently. 
• 2 is the only even number which is a prime number.
• All the even numbers except 2 are composite numbers. (Why?)

The number '1' is neither a prime number nor a composite number. It is called as a Unique number. (Can you think why?)

Here, we discussed about the types of numbers decided on the basis of the number of factors they have. In the next post, we will see how to find factors of a given number.