## Thursday, September 13, 2007

### Weird Numbers

The world is full of weird things like numbers. A prime number is any number that can only be divided by itself and 1. The single digit prime numbers are 1, 2, 3, 5, 7 as they can only be divided by themselves and 1. 1 will divide evenly into any number odd or even. 2 will only divide into even numbers such as 0, 2, 4, 6, 8 in the first column (10, 12, 14, 16, 18). 5 will divide evenly into any number ending in 0 or 5 in the first column like 40 or 25. 3 will not always divide evenly into any number from 1 to 9 in the first column.. For instance 3 will divide evenly into 33 but not 43. 7 will not always divide evenly into any number that has numbers from 1 to 9 in the first column. 7 will divide evenly into 7 but not 47. There are 5 one column prime numbers. ( 1, 2, 3, 5, 7 ). If you go to two column prime numbers ( 11, 13, 17, 19 ) you will see that 1, 3, and 7 are all prime numbers in the first column but 9 ( 3 X 3 ) isn’t a prime number. You will soon discover that this pattern follows in the first column for all prime numbers. In other words if a number is a prime it will end in 1, 3, 7 or 9 in the first column. The rub, of course, is not all numbers ending in 1, 3, 7 or 9 are prime numbers. 21, 33, 27, 39 aren’t prime numbers.

Eulalia said...

Great work.