Wonderful digital black hole Wonderful digital black hole Wonderful digital black hole A wonderful digital black hole was originally a concept in astronomy, indicating such a celestial body: its gravitational field is so strong that even light cannot escape. Borrowing words from mathematics refers to some kind of operation, which is generally limited to starting from some integers. After a certain specified operation, the result will inevitably fall into a "digital black hole." 111,black hole black hole 6174617461746174 Look at the following formula: 9863-. 8532-2358=6 174; 73 1 1- 1 137=6 174; 6640-0466=6 174; 6200-0026=6 174; 742 1- 1247=6 174; 9973-3799=6 174; ..... find their magic? Please write a four-digit number at will. It doesn't matter whether the four digits of this number are the same or not, but these four digits are not allowed to be exactly the same, nor are they allowed to have exactly the same trend. For example, 3333, 7777 and 7337 should be excluded. After writing the four digits, rearrange the digits in the digits from big to small and from small to big, and you will get the largest and smallest of the four digits, and subtract them to get the other four digits. Perform the same transformation on the four numbers that make up this four-digit number, then get a maximum number and a minimum number, and then subtract them ... So on, after several transformations (up to 7 times), you will definitely get 6 174. Is this an accident? Let's give a random number 133 1 and do it continuously according to the above method: 331133 = 2178 8721-1. The "ghost" of 6 174 appeared again. You might as well try. For any four-digit number with incomplete numbers, it is bound to fall into the trap to calculate at most 7 steps. Indian mathematicians have proved the number of black holes. The magic number 6 174 is a black hole generated in the number, which seems to have a magical power. 222,,, three digits also have such a digital black hole black hole black hole 495495495495495: 495. Find a random number, such as 297. The numbers on the three-digit number are arranged from small to large, and they are 972 and 279 respectively. Subtract (972-279) to get 693. Do it again as above, 963-369 gets 594, do it again, 954-459 gets 495. Besides, there are other digital black holes: 5-bit black hole 53955, 599946-bit black hole 63 1764, 549945-bit black hole 9750842 1, 633 17664-bit black hole 975308642 1. These numbers will be sucked in by 6 174 through one operation. We call this number the black hole number.