Special case of 1, prime numbers are kind of theseīuilding blocks of numbers.

Of them, if you're only divisible by yourself and

Irrational numbers and decimals and all the rest, just regularĬounting positive numbers. Not including negative numbers, not including fractions and That you learned when you were two years old, not including 0, Numbers- numbers like 1, 2, 3, 4, 5, the numbers So it has four naturalĮxactly two numbers that it is divisible by. Try a really hard one that tends to trip people up. So once again, it's divisibleīy exactly two natural numbers- 1 and 5. But it is exactlyĭivisible by 5, obviously. You could divide them into it,īut you would get a remainder. So it does not meet ourĬonstraints for being prime. Well, 4 is definitelyĭivisible by 1 and 4. It's not divisible by 2, soģ is also a prime number. And it's really not divisibleīy anything in between. Well, 3 is definitelyĭivisible by 1 and 3. And 2 is interestingĪny other even number is also going to beĭivisible by 2, above and beyond 1 and itself. That color for the- I'll just circle them. It in a different color, since I already used Two natural numbers- itself, that's 2 right there, and 1. So 2 is divisible byġ and by 2 and not by any other natural numbers. So 1, although it might beĪ little counter intuitive is not prime. Of our definition- it needs to be divisible byĮxactly two natural numbers. So you might say, look,ġ is divisible by 1 and it is divisible by itself. And if this doesn'tĮxamples here, and let's figure out if some Want to say exactly two other natural numbers,īecause one of the numbers is itself. One of those numbers is itself,Īnd the other one is one. It is a natural number divisibleīy exactly two numbers, or two other natural numbers. It is a natural number- and a natural number, onceĪgain, just as an example, these are like the numbers 1, 2,ģ, so essentially the counting numbers startingĪt 1, or you could say the positive integers. What encryption means, you don't have to worryĪbout it right now. That your computer uses right now could beīased on prime numbers. Your mathematical careers, you'll see that there's actuallyįairly sophisticated concepts that can be built on top of

A big list of prime numbers up to 100