How to quickly check a number is Prime or Not?
Prime numbers are those numbers which are only divisible by
one and itself.
1, 3, 5, 7, 11, 13, 17...
For small numbers it is easy to say whether number is Prime
number or not. But for large number like it is difficult to check. Here is the trick that can check Prime number test within seconds.
Let the number be 89
Divide this number by 8, 9, 8+9=17 and 7+1=8
2nd
step = 89/9 not divisible
3rd
step = 89/17 not divisible
4th step =89/8
not divisible
So the number is Prime number.
Now check number 139
Note: If number
contains 1 at any position doesn’t check the number for 1.
1st step =139/3
not divisible
2nd Step = 139/9
not divisible
3rd step = 139/13 not divisible
4th step = 139/4
not divisible.
So the number is Prime number.
Now check the number 453
1st step = 453/4
not divisible
2nd Step = 453/5 not divisible
3rd step = 453/3
= 151.
Since it is divisible so the number is not a Prime number.
This tricks works for a large number also.
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