Prime-Numbers

AQUiLA MAGAZINE

MEGAMATHS

Were you blown away by how periodical cicadas are so in tune with prime numbers in the Megamaths issue of AQUILA magazine ? Did it make you feel like upping your own prime number game ? Of course it did !

A prime number is a whole number that can ’ t be divided evenly by any other number apart from itself or 1 . So , 17 is a prime number because no other number divides into it . But 18 is not a prime number , because it can be divided by 2 , 3 , 6 and 9 .

ACTIVITY SKILLS

45 mins to 1 hr

Record breaker

Prime numbers don ’ t occur with any kind of pattern , so there ’ s no formula to find them . Instead , they have to be discovered one by one ! Computers are now used to help in the search . The largest known prime number was found in December 2018 :

282,589,933 – 1

This means multiplying 2 by itself 82,589,933 times and then subtracting 1 . You ’ d need a lot of paper to write it out , as this whopper of a prime number has almost 25 million digits !

DIFFICULTY

YOU WILL NEED

o Print out of grid ( on page 3 ) or paper and pencil

The Sieve of Eratosthenes

Without a supercomputer , here ’ s an easy way to find smaller prime numbers . It ’ s called the Sieve of Eratosthenes , named after an ancient Greek mathematician ( and not a really nice kitchen sieve ). We ’ ll use it on the first 100 numbers . You can leave out the number 1 , which isn ’ t strictly a prime number .

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