There are **89** NRICH Mathematical resources connected to **Properties of numbers**, you may find related items under Numbers and the Number System.

What do you see as you watch this video? Can you create a similar video for the number 12?

Are these statements always true, sometimes true or never true?

This is a game in which your counters move in a spiral round the snail's shell. It is about understanding tens and units.

Look at three 'next door neighbours' amongst the counting numbers. Add them together. What do you notice?

This problem looks at how one example of your choice can show something about the general structure of multiplication.

This investigates one particular property of number by looking closely at an example of adding two odd numbers together.

If you have ten counters numbered 1 to 10, how many can you put into pairs that add to 10? Which ones do you have to leave out? Why?

Each light in this interactivity turns on according to a rule. What happens when you enter different numbers? Can you find the smallest number that lights up all four lights?

These spinners will give you the tens and unit digits of a number. Can you choose sets of numbers to collect so that you spin six numbers belonging to your sets in as few spins as possible?

Mr Gilderdale is playing a game with his class. What rule might he have chosen? How would you test your idea?

Nearly all of us have made table patterns on hundred squares, that is 10 by 10 grids. This problem looks at the patterns on differently sized square grids.

Can you each work out the number on your card? What do you notice? How could you sort the cards?

How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?

Choose four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?

My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?

A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly £100 if the prices are £10 for adults, 50p for pensioners and 10p for children.

How many six digit numbers are there which DO NOT contain a 5?

The number 2.525252525252.... can be written as a fraction. What is the sum of the denominator and numerator?

Complete the following expressions so that each one gives a four digit number as the product of two two digit numbers and uses the digits 1 to 8 once and only once.

The diagram illustrates the formula: 1 + 3 + 5 + ... + (2n - 1) = n² Use the diagram to show that any odd number is the difference of two squares.

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

Is there an efficient way to work out how many factors a large number has?

I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?

Can you find examples of magic crosses? Can you find all the possibilities?

Can you find any two-digit numbers that satisfy all of these statements?

Guess the Dominoes for child and adult. Work out which domino your partner has chosen by asking good questions.

This article introduces the idea of generic proof for younger children and illustrates how one example can offer a proof of a general result through unpacking its underlying structure.

A case is found with a combination lock. There is one clue about the number needed to open the case. Can you find the number and open the case?

Charlie has made a Magic V. Can you use his example to make some more? And how about Magic Ls, Ns and Ws?

Which numbers can we write as a sum of square numbers?

Can you find some Pythagorean Triples where the two smaller numbers differ by 1?

Skippy and Anna are locked in a room in a large castle. The key to that room, and all the other rooms, is a number. The numbers are locked away in a problem. Can you help them to get out?

Sets of integers like 3, 4, 5 are called Pythagorean Triples, because they could be the lengths of the sides of a right-angled triangle. Can you find any more?

Take three whole numbers. The differences between them give you three new numbers. Find the differences between the new numbers and keep repeating this. What happens?

Robert noticed some interesting patterns when he highlighted square numbers in a spreadsheet. Can you prove that the patterns will continue?

Here is a machine with four coloured lights. Can you make two lights switch on at once? Three lights? All four lights?

Imagine a machine with four coloured lights which respond to different rules. Can you find the smallest possible number which will make all four colours light up?

This task depends on learners sharing reasoning, listening to opinions, reflecting and pulling ideas together.

I am thinking of three sets of numbers less than 101. Can you find all the numbers in each set from these clues?

I am thinking of three sets of numbers less than 101. They are the red set, the green set and the blue set. Can you find all the numbers in the sets from these clues?

Can you each work out the number on your card? What do you notice? How could you sort the cards?

Can you find ways of joining cubes together so that 28 faces are visible?

Here is your chance to investigate the number 28 using shapes, cubes ... in fact anything at all.

Can you make a hypothesis to explain these ancient numbers?

Try to solve this very difficult problem and then study our two suggested solutions. How would you use your knowledge to try to solve variants on the original problem?

Ranging from kindergarten mathematics to the fringe of research this informal article paints the big picture of number in a non technical way suitable for primary teachers and older students.

Bernard Bagnall recommends some primary school problems which use numbers from the environment around us, from clocks to house numbers.

If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?