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The semiprime 9986831781362631871386899 = 2048903657 * 4874232005610907 is the largest of the 203 positive integers N such that for some integer d => 2 this number is a ddigit palindrome base 10 as well as a ddigit palindrome for some base b different from 10. Curiously, the smallest such integer, 22, and the number of solutions 203 = 7 * 29, are also semiprimes. [Post]
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