The peculiarity of the number 6.174 which surprises the mathematicians

It turns out that in 1949, the Indian Dattatreya Ramchandra Kaprekar revealed at the Madras Mathematical Conference grades of 6,174 and created the Constant of Kaprekar.

According to the expert, with a maximum of seven steps between addition and subtraction, 6.174 should be achieved.

The operation includes the following steps:

1. Choose any four-digit number (with limited exceptions, see below)
2. Sort these four numbers in descending order, to get the minuend of a subtraction
3. Sort these four numbers in ascending order, so as to be subtracted from the same subtraction
4. Calculate the rest by subtracting the subtraction of the minuend
5. If the rest does not give 6.174, repeat the previous steps, adding zeros to the right at least and left to subtracting, whenever necessary to complete the four digits.

By doing this sequence and not repeating it more than seven times, the result will be 6174.