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25,011 is Special

Michael Filaseta, University of Sounth Carolina, has shown that 25,011 is a very special number. And, there are infinitely more numbers akin to 25,011...we just do not know them all yet.

First, 25,011 is a "nonprime" number, in that you can insert any digit 0-9 anywhere you want into it, and it will remain nonprime. That is, 925,011 or 250,011 or 250,151..etc. are all nonprime numbers.

Now, Filaseta and his student Mark Kozek have proven that there are infinitely many such nonprimes that are odd and don't end in the digit 5. And 25,011 is special because it is the smallest one.

Source: S. Begley's "Number Proofs Done by Computers Might Error," Wall Street Journal, 1/12/07