1 7 is prime
2 13 is prime
3 97 is prime
4 103 is prime
5 997 is prime
6 1003=17*59
7 9997=13*769
8 10003=7*1429
9 99997=19*19*277
10 100003 is prime
11 999997=757*1321
12 1000003 is prime
13 9999997=7*1428571
14 10000003=13*769231
15 99999997=1297*77101
16 100000003=643*155521
17 999999997=71*2251*6257
18 1000000003=23*307*141623
19 9999999997=13*769230769
20 10000000003=7*1428571429
21 99999999997=17*5882352941
22 100000000003 is prime
23 999999999997=5507*181587071
24 1000000000003=61*14221*1152763
25 9999999999997=7*7*56527*3610339
26 10000000000003=13*29*547*48492137
27 99999999999997=839*119189511323
28 100000000000003=19*31*613*276964579