> For the complete documentation index, see [llms.txt](https://shreeshail.gitbook.io/c-dac-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shreeshail.gitbook.io/c-dac-notes/appitude.md).

# Number System

* How number is made

```
25	=	2	5
	=	20*10 + 5
	=	25
	
xy	=	10x+y
yx	=	10+x
	
679	=	
face value of 7 is 7
Place value of 7 is 10*7=70 
```

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### Natural No

* 1,2,3 .... infinity

### Whole No

* 0,1,2,3 ... infinity

### Integer

* infinity ... -3,-2,-1,0,1,2,3...infinity
* 4.8 is not a integer
* so the integer value of 4.8 is 5.

### Prime No

* The number is divisible by itself and 1.
* 2,3,5...
* 1 to 100- 25 prime no
* Three digit smallest prime no 101

### Composite Number

* The number which are not prime they are composite number

### Co-prime number

* If the HCF of two number become 1 then they are co-prime
* eg (8,15)

***

Compiled by [Shreeshail Vitkar](https://github.com/shreeshailaya)

Feel free to fork @ [C-dac Notes](https://github.com/shreeshailaya/c-dac)

***