Determine whether the following

numbers are prime, composite, or neither. So just as a bit of

review, a prime number is a natural number– so one of

the counting numbers, 1, 2, 3, 4, 5, 6, so on and so forth–

that has exactly two factors. So its factors are 1 and itself. So an example of a

prime factor is 3. There’s only two

natural numbers that are divisible into 3– 1 and 3. Or another way to think about

it is, the only way to get 3 as a product of other

natural numbers is 1 times 3. So it only has 1 and itself. A composite number

is a natural number that has more than just

1 and itself as factors. And we’ll see examples of

that and neither– we’ll see an interesting case

of that in this problem. So first let’s think about 24. So let’s think

about all of the– I guess you could think of

it as the natural numbers or the whole numbers,

although 0 is also included in whole numbers. Let’s think of all of the

natural counting numbers that we can actually

divide into 24 without having any remainder. We’d consider those the factors. Well, clearly it is

divisible by 1 and 24. In fact, 1 times

24 is equal to 24. But it’s also divisible by 2. 2 times 12 is 24. So it’s also divisible by 12. And it is also divisible by 3. 3 times 8 is also equal to 24. And even at this point,

we don’t actually have to find all of the factors

to realize that it’s not prime. It clearly has more factors

than just 1 and itself. So then it is clearly

going to be composite. This is going to be composite. Now, let’s just finish factoring

it just since we started it. It’s also divisible by 4. And 4 times 6– had just

enough space to do that. 4 times 6 is also 24. So these are all of the

factors of 24, clearly more than just one and 24. Now let’s think about 2. Well, the non-zero whole numbers

that are divisible into 2, well, 1 times 2

definitely works, 1 and 2. But there really

aren’t any others that are divisible into 2. And so it only has two

factors, 1 and itself, and that’s the definition

of a prime number. So 2 is prime. And 2 is interesting because it

is the only even prime number. And that might be

common sense you. Because by definition, an

even number is divisible by 2. So 2 is clearly divisible by 2. That’s what makes it even. But it’s only

divisible by 2 and 1. So that’s what makes it prime. But anything else

that’s even is going to be divisible by

1, itself, and 2. Any other number

that is even is going to be divisible by

1, itself, and 2. So by definition,

it’s going to have 1 and itself and something else. So it’s going to be composite. So 2 is prime. Every other even number

other than 2 is composite. Now, here is an

interesting case. 1– 1 is only divisible by 1. So it is not prime,

technically, because it only has 1 as a factor. It does not have two factors. 1 is itself. But in order to

be prime, you have to have exactly two factors. 1 has only one factor. In order to be

composite, you have to have more than two factors. You have to have 1, yourself,

and some other things. So it’s not composite. So 1 is neither

prime nor composite. And then finally we get to 17. 17 Is divisible by 1 and 17. It’s not divisible by 2,

not divisible by 3, 4, 5, 6. 7, 8, 9 10, 11, 12,

13, 14, 15, or 16. So it has exactly two

factors– 1 and itself. So 17 is once

again– 17 is prime.

yay first viewer π but you guys r great ive learned alot from your lessons keep it up π

how.. are you so smart?

nice π

{ so smart}

I like the way you repeat certain words and sentences when you write. somehow it helps memorizing things

this is awesome (except i'm watching this for school

hi

I just have to say that I just love your videos! I'm teaching 6th grade math this year and you have helped me so much.

You could argue it's neither, it's composite 0/x is 0 but it cannot be divided by itself so a different kind of neither to 1.

What is an "un-natural" number?

is 325 prime or composite?

like it

He's better at teaching than my real teacherπΆ

I have a problem, They never let me do anything like 2 24 72 1 34 ect, they threw me straight into 179 734 ect its ridiculous.

thank you. . .

U

I'm your student Mia you may not remember me . Waaaaaaaaaaaawaaaaaaaawaaaaaaaawaaaaawaaaaa !!!!!!!!!!!!!!!! ππ’π₯

I am your student but I still need help with prime numbers

Awesomeπππ

VERYclearly explainedis this for grade 4

Thank you u helped with my finals

Omg thanks we barely covered prime and composite

i need more examples on composite number.

basically the difference between prime number and composite number.

hi

thanks i have a test on this tomorrow

This helps a lot.

What grade is this for?

4th grade

im 23 and i never understood this now i do thank you

THANK YOU!!!This video has a caption of over 30 languages. SiCK!

thank you do much this is going to help SOOO much

All thanks to Sal Khan! thank u soooo much

Thanks I needed to learn that

please check 13233435631 is a composite number

Gang gang

So tu tu

you said a prime is one itself how 59 is a prime number?

Musalman murdabad

You can get the same as the same as the same as the same as the same as last year we had a chance to see if it is not

Thanks sir

Thank you again.

>β’< mewo

Itβs good practice, thanks

These Khan math videos are on POINT! learning more here than from the instructor

2019 anyone?

This really helped !!

I watched on 5 other videos this ones the best

I clicked on this bc it helps me understand better than my homeschool vids

~~w~~Learning thia at school π