Quick tip to see if a number is prime

A simple test to see if a number is prime or composite. All you do is find the square root of the number. Next, find all the prime numbers of this number. If none of these prime numbers are a factor of the number then the number is prime.

[@matiaspereira9382]

If you want to find out if a big number is prime or composite you have to find out its square root and divide it by all prime numbers smaller than its square root. If the number is divisable by any of the prime numbers then the number is composite but if the number isn't divisable by any of the prime numbers then the number is a prime

[@nietocurcio]

Thank you, it helps a lot. I was solving a programming problem, and I think that we should check all prime numbers

[@andrewciccarone5784]

I'm guessing you were also working on comp sci

[@viperdruid]

you can check if the sqrt is a whole number then if it is a whole number the number automatically becomes non prime and if the number isnt whole then you can check the divisibilty using all the whole numbers less than the sqrt except 1

[@ajboysen1]

Funny. I finding things to practice my programming skills with and am deciding to build a twin prime finder

[@metayoutubeacademy]

this video recomended by google after searching "fastest way to know if the number is prime"... it helped me alot thats why i come to comment here to say thak you.... this video deserve millions and trillions of likes and views

[@HarshYadav-cj3yu]

thanks for such a great lesson. I really appreciate that

[@vschannel7198]

Thanks. Your trick makes sense. The other 6j-1 and 6n+1 is not that efficient. Thanks a lot

[@jtteope1178]

High school: Thank you this helped a lot Grade 3: *CONFUSED*

[@PBadasie]

Yes since I’m in grade 6 now and we didn’t learn square root yet

[@DPME820]

@@PBadasie I am going to go to Grade 9, in a week. This video helped me a lot

[@deffman32tech]

​@@DPME820grade 12 here, I guess it really helps across the board

[@DPME820]

@@deffman32techYeah! I am officially grade 9 now. The entire schooling system which I have been used to has completely changed now. Now we have to worry about something called portfolios!?!

[@deffman32tech]

@@DPME820 lol good luck with that

[@AbhinavChalla]

Thank you sooooo much, it is very helpful

[@thomaservin1669]

Just memorize several dozen primes. It is slightly worth knowing. Note also: all primes are odd numbers, except 2. All even numbers are not primes. No primes end in zero, nor 5. This bit of trivia can help you to identify non-primes, at least. So all primes end in 1, 3. 7, or 9 (the reverse is not true though

[@user-vp4nx1bj3v]

This makes it very easy thank you!

[@TejasChavan3041]

Good trick, thank you 👍🏻

[@robertodelaprieta8842]

The statement "For any composite number (X) it's prime factors must be less than the square root of the number" in 0:25 is NOT TRUE. Take, for instance, 14 = 7x2 15 = 5X3 It is however true that "every composite number has a prime factor less than or equal to its square root".

[@NameOptional-rt9hp]

Thank you. Came here looking for this correction.

[@rubenyanez5645]

first tip is useless, any number that has a perfect square we can automatically deduce that that is not prime

[@atheist_ghost]

Thank you so much ❤️❤️

[@Ryan-science-history]

How can we determine if 1009 is a prime number? According to this method, root of 1009 is about 31 so we need to divide the prime numbers from 0 to 31? It is really hard to calculate.

[@rubenyanez5645]

for finding the square root of the number, wouldn't it be better to say the first step is to find the closest perfect square above that number?

[@gregaylmer5089]

Definitely quicker!

[@haroldhobson6503]

Once you get to larger numbers (eg. 227), you would probably have to use a calculator to find your perfect square, so if you can't do it without a calculator, you might as well calculate the square root. Makes it quick and easy.

[@vibodhj349]

awesome trick! this helps

[@sabrinashamme9419]

Thank you very much ❤

[@beautywitch279]

Thank you sooooo much it is so helpful 💖

[@MooMooMath]

Glad it was helpful!

[@momengamer3517]

helped me a lot thx

[@rksidol8142]

Thank you so much sir 🥰

[@sabikikasuko6636]

I don't think a methodology for finding prime numbers that requires knowing which numbers are prime is very useful...

[@santinicounsel9023]

you literally just have to memorize a couple prime numbers to unlock them all

[@rossanaleblanc]

Good method but I will inform you, or maybe you forgot, there is a very easy test for finding out if a number is divisible by three: add up the digits and they must be divisible by 3. So 9+7=16 and 2+9=11 tell me neither 97 nor 29 are divisible by 3.

[@doctorkk1939]

This is test of divisibility

[@thissunchild]

​@@doctorkk1939which tells whether a number is a prime number

[@thissunchild]

Totally agree. For me, this was too roundabout. This is how I taught my younger class

[@Private-Joker_34]

^

[@guddinagar9486]

Thank you so much. This comment on this video is more helpful than the video itself 😅❤

[@user-ud5cv3hd7j]

question: what about for really, really big numbers, like 2958723495732098573401?

[@tiktikjeihani5394]

Do i miss something or it doesn't work for 9. Square root of 9 is 3. Prime less than 3 is 2. 9 is not divisible by 2. So 9 is prime?

[@nerdykillr494]

bro broke the system

[@jacpa2011]

square root of 9 is *3* and 9 is divisible by 3, i think he meant under OR equal to

[@itz_jenjelly]

There's an super Easy way to do this In which you have to Remember that the number which only have a 2 factors 1 and the number itself is called prime number so if we will take the example of 167 it is a prime number as it only has 2 factors which are 1 and the number itself 😊. And If you want To find out that the number is composed or not that you have to just remember that composite numbers are the numbers that have more than 2 factorso they are called composite numbers we can take the example of 161 because it has more than 2 factors

[@ishita8758]

you deserve a noble prize for this 👌

[@rolitiwari0909]

Nice trick

[@necrosudomi420thecuratorof4]

thanks bro! very clear, i know know the fundamental reason of prime. It mean you did a good job :)

[@MooMooMath]

Glad it helped

[@keniiboowilliams9673]

Thank you💯

[@MooMooMath]

You're welcome!

[@jalilp123]

You can quickly check if 3 is a factor by checking if the sum of all the digits is divisible by 3

[@jayashreee1]

Why should we use that method

[@unknowneverything1156]

The best video 👍

[@shiv.shankar]

Thank you sir. It was a very helpful video 😊

[@dd-hi1dm]

How to know if a large no. Is prime no for example 1237

[@iamamp3pimp]

Same concept applies.

[@SIDEKICKONYOUTUBE]

im confused ... 36 is a prime number ? 36 has a lot of factors making it composite.

[@pious007]

its not, since its clearly divisible by 2 and 3, while other numbers in the example like 97 is not divisible by 2,3,5,7 so its a prime

[@SIDEKICKONYOUTUBE]

@@pious007 yeah i may have been confused with the explanation. i thought he said 36 must be prime.

[@ceanpick4271]

Thank u sir

[@MooMooMath]

Welcome

[@panatypical]

Now let's not go gettin' too brainy....

[@gmanidweep]

nice

[@MooMooMath]

Thanks

[@nicko-shaeharvey9417]

Good Hop

[@RayyanIslam07]

What about 49? 😂

[@bethbartlett5692]

😶 I would rather pick out Prime Rib! But thanks for the offer. No Prime Numbers for this dual brain thinker ... My left is only 2 points ahead of my right and I'm BLONDE 😁 MATH: Add, Subtract, Multiply, Divide, Algebra, "fractions, decimals, & %" Then skip to Sacred Geometry , the Golden Ratio, and Fibbonaci Sequence. All other Math relatives get batched in the "No Thank You, See My Sister for Math" ... course, she can't pick out Paint Colors and her environment is quite bland. But she's your girl for Math ... I got the Canvas and Brushes. 😁🎨

[@MooMooMath]

Nice comment hope the video helped

[@krumfy7201]

this is wrong, it dont have to be divisible by only 2, 3, or 5. For example, 289 is composite while not being able to be divided by 2, 3, or 5(17x17=289)

[@jacpa2011]

what about 2,3,5,7,11,13,17? they said square root the number, then take all the prime numbers UNDER (or equal to) THE SQRT OF THE NUMBER, not only 2 3 or 5

[@tejas-pq4lt]

29 is prime?!!???

[@dd-hi1dm]

Presuming one knows square root of 29? Weird

[@lindamcd1217]

Get close 5x5, not over though. I like this

[@shakshijoshi9303]

29>25 which is the square root of 5 and 29

[@adhipatel3093]

I’m the newest comment

[@sehrishahmed3313]

Really long and boring badd

[@dd-hi1dm]

Disliked😶