6174 - The Sudoku
(Published on 15. August 2026, 21:26 by Philipp Huber)
Foreword:
The number 6174 is also known as Kaprekar's constant. It is the fixed point of the Kaprekar routine which iteratively sorts the digits of any given number into descending and ascending order and generates the new starting number by calculating the difference between these two numbers. Example (starting with the number 1678):
8761 - 1678 = 7083
8730 - 0378 = 8352
8532 - 2358 = 6174
Rules:
Blue cages are Kaprekages. The number given in the upper left corner of a Kaprekage is the result of one single iteration of the Kaprekar routine performed on the digits within the respective cage.
The red cage is a killer cage. The value of the digit within is given by the killer sum, which must be deduced as part of the solve.
Digits in grey circles are odd, the digit in the grey square is even.
Normal sudoku rules apply.
The number 6174 is also known as Kaprekar's constant. It is the fixed point of the Kaprekar routine which iteratively sorts the digits of any given number into descending and ascending order and generates the new starting number by calculating the difference between these two numbers. Example (starting with the number 1678):
8761 - 1678 = 7083
8730 - 0378 = 8352
8532 - 2358 = 6174
Rules:
Blue cages are Kaprekages. The number given in the upper left corner of a Kaprekage is the result of one single iteration of the Kaprekar routine performed on the digits within the respective cage.
The red cage is a killer cage. The value of the digit within is given by the killer sum, which must be deduced as part of the solve.
Digits in grey circles are odd, the digit in the grey square is even.
Normal sudoku rules apply.
Play online via sudokupad.
Solution code: Fifth row and fifth column (18 digits).
Solved by SKORP17, Lucythehippo, claymategirl, steperlich
