Prime numbers

[hitler didi]

Is 263 a prime number?
how can we get to know that a number is prime i know a prime number is the one which can only be divided by the number itself or by 1 but is there a shortcut for such big questions.??:x

 

[Yogi]

\(\displaystyle \sqrt{263}\)=16.217 so we only have to check prime numbers less than 16, fortunately there are only 6.

263/2
263/3
263/5
263/7
263/11
263/13

None of these produce integer results so 263 is prime.

On a calculator if you are fast/accurate this takes less than 30 seconds, so I wouldn't exactly call this a "big question".
An alternative lazier way would be looking it up on a table of primes, you can easily find a table that goes up to 100,000 or more.

 

[hitler didi]

\(\displaystyle \sqrt{263}\)=16.217 so we only have to check prime numbers less than 16, fortunately there are only 6.

263/2
263/3
263/5
263/7
263/11
263/13

None of these produce integer results so 263 is prime.

On a calculator if you are fast/accurate this takes less than 30 seconds, so I wouldn't exactly call this a "big question".
An alternative lazier way would be looking it up on a table of primes, you can easily find a table that goes up to 100,000 or more.

thanks a lot i understood the question and next time if we need to check prime numbers we should frist take out the square root and then check that if the answer is a multiple of the prime numbers below the answer
thanks a lot once again

 

[hitler didi]

Try using Google; save yourself lots of time; here:

http://www.google.ca/#hl=en&sugexp=...pw.r_qf.&fp=283e567e37122596&biw=1024&bih=571

Thank u

 

[cb123]

math

Is 263 a prime number?
how can we get to know that a number is prime i know a prime number is the one which can only be divided by the number itself or by 1 but is there a shortcut for such big questions.??:x

how did you find this out

 

[HallsofIvy]

Is 263 a prime number?
how can we get to know that a number is prime i know a prime number is the one which can only be divided by the number itself or by 1 but is there a shortcut for such big questions.??

how did you find this out

That was the definition of "prime number".

 

[lookagain]

I know a prime number is the one which can only be divided by the
number itself or by 1 . . .

Prime number: a positive integer that has exactly two distinct positive divisors







Edit: This is to note that I replaced the word "which" with "that." This was
done after reading mmm4444bot's post that follows this post.

 

[mmm4444bot]

Prime number: a positive integer which has exactly two distinct positive divisors

I like this definition (except I would write 'that' instead of 'which' ); I don't see it often.