WHAT IS THE PRIME NUMBER?

Prime Number

Definition:

1^st definition: A number which has only two distinct factors is called Prime Number.

2^nd definition: In other words, A number which is divided by only 1 and itself is called Prime Number.

NOTE :- If we consider only  2^nd definition then we can say 1 is also prime number because 1 can be divided by 1 and itself also but

          1 does not follow 1^st definition that prime number has only 2 distinct factors.

So, we will say that 1 is not a prime number.

Remember that if we say only 2^nd definition, it will be called uncomplete definition. So, 1^st definition is very important to define prime number.

 

Some facts about Prime Numbers:

Ø   2 is the smallest prime number.

(Note: 2 is one and only prime number which is even prime number).

Ø 3 is the smallest odd prime number.

Ø There are only nine (2,3 5, 7, 11, 13, 17 ,19, 23) prime numbers between 1 and 25.

Ø There are only six (29, 31, 37, 41, 43, 47) prime numbers between 25 and 50.

Ø There are only 10 (53, 59, 61, 67, 71, 73, 79, 83, 89, 97) prime numbers between 50 and 100.

Ø Thus, there are only 25 prime numbers between 1 and 100.

Ø
This happens only one time between 1 and 100 when we can see 7 consecutive non- prime numbers which are from 90 to 96 (7 consecutive non-prime numbers)

 

 

Ø The Great Internet Mersenne Prime Search (GIMPS) has discovered the largest known prime number, 2^82,589,933-1, having 24,862,048 digits.

Ø Except 2, if we add any two prime numbers, we will get a positive even integer.

Ø For example,

3(prime number) + 5(prime number) = 8(even integer number).

You can also try with another example.

 

 

 

Thanks & Regards

Anurag Sharma

(AAA tutorial)