## Numbers from one to thirty-one ... a page for each day of the month

... and for similar facts about other numbers see Numbers: Facts, Figures & Fiction.

# 17

17 is a prime number.

In 1963 the Italian film director Federico Fellini released an autobiographical film Eight and a Half. A few years later a film called Seventeen was released and one film critic, who could not resist making a comparison, headed his newspaper review 'Seventeen - twice as good as Eight and a Half".

Under British law, when you reach the age of 17 -

• criminal charges against you will be dealt with in the adult courts,
• you can hold a licence to drive most vehicles,
• you can buy or hire any firearm or ammunition.

If you look carefully at wallpaper you will always find that the pattern repeats. You also find repeating patterns on printed fabric. Mathematicians have discovered 17 different types of repeating pattern (called plane symmetry groups). Each type is different in the way it repeats - not in the colour or the shape of the pattern. If you had to wallpaper a house for a mathematician, you might use a different one of the 17 repeating patterns on each wall.

Updated 28 November 2003