A prime number is a number that deserve to only be split by itself and also 1 there is no remainders. Below we explain what precisely this means, provide you a perform of the prime numbers kids need to understand at main school and carry out you through some practice prime number questions and examples.

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What is a prime number?

A prime number is a number greater than 1 with only two components – themselves and also 1.

A prime number can not be separated by any other numbers without leaving a remainder.

An instance of a prime number is 13. It have the right to only be split by 1 and 13. Dividing a prime number by one more number results in number left over e.g. 13 ÷ 6 = 2 remainder 1.

15 is not an example of a prime number because it deserve to be separated by 5 and 3 and by itself and 1.

15 is an example of a composite number because it has much more than 2 factors.

Prime number examples

How to occupational out if a number is a prime number or not.

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What room the prime numbers?

There room 8 element numbers under 20: 2, 3, 5, 7, 11, 13, 17 and 19.

The very first 10 prime numbers room 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.

There space 25 prime numbers between 1 and 100.

Prime numbers can continue well past 100. For example, 21,577 is a prime number.

List of prime numbers to 100

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.

Smallest prime number

2 is the the smallest prime number. It also the only even prime number – all other also numbers deserve to be split by themselves, 1 and also 2 at least, an interpretation they will have actually at the very least 3 factors.

Largest prime number

One the the most famed mathematicians the the classic era, Euclid, recorded a proof that there is no largest prime number. But many scientists and also mathematicians room still searching to find it as component of the an excellent Internet Mersenne prime Search.

Thelargest well-known prime number(as the November2020) is282,589,933− 1, a number which has 24,862,048 digits once written in basic 10. Prior to then the largest known prime number to be 277,232,917-1, having 23,249,425 digits.

By the moment you review this it may be also larger, however you deserve to follow its progression on Wikipedia.

Common FAQs about prime numbers


Is 1 a element number

1 is not a element number due to the fact that it has only one factor, namely 1. Element numbers must have precisely two factors


Is 51 a prime number?

51 is no a element number due to the fact that it deserve to be split by 3 and 17, and also by itself and 1. Ie it has four factors.



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Prime numbers in primary school

Prime numbers space not introduced in the UK until Year 5.

According to the national Curriculum, Year 5 children should be taught to

“know and also use the vocabulary of element numbers, prime factors and composite (non-prime) numbers to develop whether a number up to 100 is prime and recall prime numbers approximately 19.”

In Year 6, youngsters should be able to“identify usual factors, usual multiples and also prime numbers”.

How are prime numbers used in the genuine world?

One that the most important uses for prime numbers is in cyber security – making details shared over the internet safer.

In order come encrypt (make secure) things like credit card details, clinical records, even some messaging services prefer WhatsApp, software engineers make algorithms making use of prime numbers.

By multiplying 2 very large prime numbers together (some carriers use element numbers that are hundreds of digits long!), we develop an even larger number who original components (the two very huge prime numbers) are only well-known to us. We then use this also larger number come encrypt our information.

If anyone else wants to discover what information we room sending, they have to uncover out what ours original factors were. With prime numbers as lengthy as the persons we have used, it can take them year or even years of consistent trial and also error before they find even one. This ensures our details is retained safe.

Wondering about how to define other crucial maths vocabulary to your children? inspect out our major Maths Dictionary, or shot these main maths terms:

Prime number questions

1) A square number and a element number have a total of 22. What space the 2 numbers?

A: 9 and also 13

2) Emma thinks of 2 prime numbers. She to add the two numbers together. She answer is 36. Create all the possible pairs of element numbers Emma can be thinking of.

A: 3 and also 33; 5 and 31; 7 and also 29; 13 and also 23; 17 and 19

3) one the 2 prime numbers – 29, 59, 39, 69, 29

A: 29 and 59

4) compose the 3 prime number which main point to do 231.

A: 3 x 7 x 11

CHALLENGE QUESTION: Chen choose a prime number. That multiplies it by 10 and then rounds it come the nearest hundred. His answer is 400. Write all the possible prime numbers Chen could have chosen.

A: 37, 41 or 43.

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Prime number worksheets

Prime number videos

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