Amazing Number Fact No 44
The Ultimate Palindrome
- What is a Palindromic Number? Examples are
11, 123321 and 2002. They read the same backwards as
forwards. This is the number equivalent of a Palindrome
which is a word which reads the same forwards and
backwards. Hannah is an example.
Pick a number, reverse its digits and add the
resulting number to the original number. If the answer is
not palindromic then repeat the process. For example
let's start with 87:
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Step 1:
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87 + 78 = 165
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not palindromic so...
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Step 2:
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165 + 561 = 726
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not palindromic so...
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Step 3:
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726 + 627 = 1353
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not palindromic so...
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Step 4:
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1353 + 3531 = 4884
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palindromic!
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You might like to explore the result of doing
this process to several other small numbers. Do all the
numbers that you try end up with a palindromic number?
- 196 is a particularly stubborn number. Nobody
knows whether eventually doing this reversal and adding
process with 196 yields a palindromic number. Here is a
quote from an account written by John Walker on May 25th
1990. He had written a computer program in an attempt to
determine the outcome for the number 196:
- "For almost three years the process of
reversal and addition continued. Last night,
at five minutes before midnight, the program
printed the message: 'Stop point reached on
pass 2415836. Number contains 1000000
digits.' and exited. The built-in endpoint
had been reached; after 2,415,836 reversals
and additions, 196 had grown to a number of
1,000,000 digits without ever yielding a
palindrome. Does it ever produce one? Still,
nobody knows."
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Recently computer tests have continued up to
nearly 9.5 million steps yielding a 4.9 million digit
number which is not yet palindromic! The search no doubt
continues!!
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- If you have answers, discoveries, new
questions etc to do with this Number Fact then...
- E-mail us at madrascollege.maths@fife.gov.uk
- ...and we will publish them here.
- Read our
previous Amazing
Number Facts
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