I came up with an equally unexciting activity you can use to go back to sleep – listing the numbers that divide 1000.

Here is the general method. First just list the divisors of 10 – 1, 2, 5 and 10.

Next you want the divisors of 100 that have not already been included under 10. Seem difficult? Here is a trick that makes it easy. You only need to include numbers that use two 2’s or two 5’s. Two 2’s is 4. Now keep multiplying by 5. 5×4=20 and 5×20=100. Now start with two 5’s for 25, and keep multiplying by 2 – 25, 50 and 100 has already been included.

Next we move to divisors of 1000, and we apply the same trick. Start with three 2’s = 8 and keep multiplying by 5. Then start with three 5’s = 125, and keep multiplying by 2.

With a little practice, you should be able to do 10,000 then 100,000 and, dare I say it, a million.