6174

Take any number with 4 non-repeating digits. Say 1562.Step 1: Arrange the number in ascending and then descending orderStep 2: Subtract the smaller number from the bigger number6521 - 1256 = 5265Repeat the steps with your new number (the answer):(5265 rearranged) 6552 - 2556 = 3996(3996 rearranged) 9963 - 3699 = 6264(6264 rearranged) 6642 - 2466 = 4176(4176 rearranged) 7641 - 1467 = 6174Try any 4