Let us consider a number, e.g. 1234
Now reverse the positions of the terminal digits, so we get 4231
4231-1234=2997 which is divisible by 9
i have seen this for n-digit numbers, where n ranges from 2 to 6
Is there any number which is contradicting this behavior irrespective of its number of digits?
Now coming back to the example,
Now 2997/9=333 is a palindrome
Another example 923456781-123456789=799999992
799999992/9=88888888
Is this also independent of the number of digits of the original number?
Let us consider :
95623-35629=59994/9=6666
The largest prime factor of 6666 is 101 which is a palindrome and a prime number.
Now 6666/101=66
Again 66/11(11 being the largest prime factor of 66) equals to 6 which is a palindrome.
Another example :
923456781-123456789=799999992/9=88888888
The largest prime factor of 88888888 is 137
88888888/137=648824/101(101 being largest prime factor of 648824)=6424/73(73 being largest prime factor of 6424) this in turn equals to 88 (a palindrome)
Finally, 88/11(11 being largest prime factor of 88 and a palindrome) equals to 8 which is also a palindrome.
Now as per (http://math.stackexchange.com/questions/200835/are-there-infinitely-many-super-palindromes), will it be correct to call 88888888 a super palindrome?
Can it be possible to call a number a super palindrome if it generates non palindromes along with palindromes, provided the non-palindromes finally generate using the method of division by largest prime factor, a palindrome other than 1?
Best Answer
The remainder of dividing a number by 9 is the same as dividing the sum of its digits by 9. This is one of the classic divisibility rules. The sum of digits is the same after you reverse the numbers, so the difference of the sums of digits will be zero. The difference of the numbers is therefore divisible by 9.