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Counting Factors

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

Summing Consecutive Numbers

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?

Oh! Hidden Inside?

Find the number which has 8 divisors, such that the product of the divisors is 331776.

Magic Crosses

Age 7 to 14 Challenge Level:
You can use the magic cross tester below to find magic crosses of your own.
Choose five numbers and put them in the blue boxes.
A message will appear to tell you whether your cross is magic.

Press the reset button to start again.
Reset