there are many possible answer
you just set your ones digit first for example, if your ones digit is 1 then you can find the thousands digit by multiplying it by 2 and also the number 2 is more than your ones digit which is 1 then the number 2221 is one of the possible 4 digit number fitting the question above.. heres other numbers
4332
6443
8554
2231
2981
4982
6763