Eric the mathematician knows a trick that will amaze you! No matter what number you choose, you will always end up with the same result. It's not magic ... it's mathematical! The educational side: The number 6 174 is very mysterious. In 1949, the Indian mathematician, DR Kaprekar, formulated a process called Kaprekar's constant. Step 1: choose a four-digit number, making sure that at least one digit is different from the others. Step 2: rearrange the digits, first in descending order, then in ascending order. Step 3: Subtract the smaller number from the larger number. Repeat steps 2 and 3 with the resulting number. Continue until you always arrive at 6,174: a constant, because after that the number remains the same.