# What are prime numbers?

3 min readstudies **Prime numbers** Its history goes back many centuries ago and this set of numbers has always brought a lot of curiosity to scholars. Knowing what a prime number is and how to determine it can make it easier to solve math questions in your proofs, so follow this article for a full explanation.

## What are prime numbers?

on the principle,** Prime numbers **They are those that can only be divided by two factors: one (1) alone.

Like, for example, the number two (2). You can just divide the number two (2) by the number one (1) or by itself, so it’s a **Cousin’s number**.

But what about number one (1)? number one (1) **Not** It is considered a prime number because it is only divisible by itself. Remember that the rule for a prime number is that it is divisible by itself **And by number 1.**

Other examples of **Cousins**: 3,5,7,11,13,17…

## How do you know if a number is prime or not?

As mentioned above, the rule is that a number is divisible by one and by itself. So knowing the basic rules of divisibility can help you determine a large number. How about remembering division rules?

**divide by 2:**All even numbers (ending in 0,2,4,6 and 8) are divisible by 2.**Divide by 3:**If the sum of their algorithms gives a number that is divisible by 3, then that number is divisible by 3.**Divide by 4:**A number is divisible by 4 if it is twice divisible by 2 or if the last two algorithms are divisible by 4.**Divide by 5:**Every number ending in 0 and 5 is divisible by 5.**Divide by 6:**If the number is even and divisible by 3, then the number is also divisible by 6.**Divide by 7:**A number is divisible by 7 if the difference between the double of the last algorithm and the remainder is a multiple of 7.

## What are the prime numbers from 1 to 100?

But how do you know all the files **Prime numbers?** How do you score the most important?

In fact, recording the main numbers in memory can speed up the solving of questions, but if you do not remember, there is a practical way to find out **Prime numbers** 1 to 100.

The system is called **Eratosthenes screen** It was created by a Greek mathematician many years ago. First, you have to write all the numbers, from 1 to 100, on a sheet of paper:

Now, you will go number by number in a very practical way. are you go:

- With
**Exception number 2**, which is already known to be a prime number, you are going to clip all even numbers. Remember that every even number is divisible by 2, so it is no longer a prime number. - Next, you must cut out all numbers divisible by 3 (except itself), according to the rule already described in the above section.
- When the number is reached
**5**, you will also cut out all numbers that are divisible by 5 – note that because you cut out even numbers, most numbers that are divisible by 5 are already deleted. - Finally, remove the numbers that are divisible by 7.

Note that prime numbers between 1 and 100 will remain, which are: **2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 e 97**.

ready! Now, you know an easy way to solve questions involving prime numbers.

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