The book is now available! 99969
(another Prime Pages' Curiosity)
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+ The largest five-digit composite number ending in 1, 3, 7, or 9 that yields no primes if the first digit is changed. I.e., 9969, 19969, 29969, 39969, 49969, 59969, 69969, 79969 and 89969 are all composite numbers.




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