"Every number ending in the digit 7 is prime." 7, 17, 37, 47, 57, and 67 are all prime, but 27 is not, so 27 is a counterexample.[[Category:Mathematics]] | "Every number ending in the digit 7 is prime." 7, 17, 37, 47, 57, and 67 are all prime, but 27 is not, so 27 is a counterexample.[[Category:Mathematics]] |