Decided to list these just for the heck of it. Some amusing almost-patterns for 10^0 + 1 through 10^19 + 1: 1 = 1 11 = 11 101 = 101 1001 = 7 * 11 * 13 10001 = 73 * 137 100001 = 11 * 9091 1000001 = 101 * 9901 10000001 = 11 * 909091 100000001 = 17 * 5882353 1000000001 = 7 * 11 * 13 * 19 * 52579 10000000001 = 101 * 3541 * 27961 100000000001 = 11 * 11 * 23 * 4093 * 8779 1000000000001 = 73 * 137 * 99990001 10000000000001 = 11 * 859 * 1058313049 100000000000001 = 29 * 101 * 281 * 121499449 1000000000000001 = 7 * 11 * 13 * 211 * 241 * 2161 * 9091 10000000000000001 = 353 * 449 * 641 * 1409 * 69857 100000000000000001 = 11 * 103 * 4013 * 21993833369 1000000000000000001 = 101*9901*999999000001 10000000000000000001 = 11*909090909090909091 10^20 + 1 is too large for my software. —Dan