Take any four digits (four digits are the same, three digits are the same, and the difference between the other digit and this number is 1,11,6566, etc.). ), recombine the four digits of this number to form the possible maximum number and the possible minimum number, and then calculate the difference between them; Repeat the same process for this difference. In the end, you always reach the black hole of 6 174 in da capra. It takes 14 steps to reach the black hole.
Extended data:
Other black holes
Black hole 1 and 123 (Sisyphus string)
Take any number and calculate its even, odd and total digits. For example, 1234567890 has five even numbers and five odd numbers, 10. In the order of "odd numbers", the new number is 55 10. Repeat the above steps to obtain T34. Repeat again to get 123.
It can be tested by computer programming. If any number is repeated a finite number of times, 123 will be obtained. In other words, not many final results can escape from the 123 black hole.
2. Narcissistic digital black hole
When the sum of all the digits of an n-digit number is equal to the number itself, this number is called a narcissistic number. Obviously, 1, 2, 3, …, 9 is a narcissistic number. There are four narcissistic numbers in the three-digit number: 153, 370, 37 1 and 407 (these four numbers are called "daffodils").
Similarly, there are four "roses" (1634,8208; 9474) and the five-digit "Five-pointed Star" (54748, 92727, 93084). When the number of numbers is greater than 5, such numbers are called "self-power numbers".
Baidu Encyclopedia-Mathematical Black Hole