7777777777

This number is a composite.

Just showing those entries submitted by 'Patterson': (Click here to show all)

7777777777 is the only ten-digit repdigit such that the product of itself and all truncations of itself minus two is prime. I.e., 7777777777*777777777*77777777*7777777*777777*77777*7777*777*77*7 - 2 is prime. [Patterson]