8161 = (2 * 4080) + 1 ;
hence not 2 divides 8161 by NAT_4:9; :: thesis:
8161 = (3 * 2720) + 1 ;
hence not 3 divides 8161 by NAT_4:9; :: thesis:
8161 = (5 * 1632) + 1 ;
hence not 5 divides 8161 by NAT_4:9; :: thesis:
8161 = (7 * 1165) + 6 ;
hence not 7 divides 8161 by NAT_4:9; :: thesis:
8161 = (11 * 741) + 10 ;
hence not 11 divides 8161 by NAT_4:9; :: thesis:
8161 = (13 * 627) + 10 ;
hence not 13 divides 8161 by NAT_4:9; :: thesis:
8161 = (17 * 480) + 1 ;
hence not 17 divides 8161 by NAT_4:9; :: thesis:
8161 = (19 * 429) + 10 ;
hence not 19 divides 8161 by NAT_4:9; :: thesis:
8161 = (23 * 354) + 19 ;
hence not 23 divides 8161 by NAT_4:9; :: thesis:
8161 = (29 * 281) + 12 ;
hence not 29 divides 8161 by NAT_4:9; :: thesis:
8161 = (31 * 263) + 8 ;
hence not 31 divides 8161 by NAT_4:9; :: thesis:
8161 = (37 * 220) + 21 ;
hence not 37 divides 8161 by NAT_4:9; :: thesis:
8161 = (41 * 199) + 2 ;
hence not 41 divides 8161 by NAT_4:9; :: thesis:
8161 = (43 * 189) + 34 ;
hence not 43 divides 8161 by NAT_4:9; :: thesis:
8161 = (47 * 173) + 30 ;
hence not 47 divides 8161 by NAT_4:9; :: thesis:
8161 = (53 * 153) + 52 ;
hence not 53 divides 8161 by NAT_4:9; :: thesis:
8161 = (59 * 138) + 19 ;
hence not 59 divides 8161 by NAT_4:9; :: thesis:
8161 = (61 * 133) + 48 ;
hence not 61 divides 8161 by NAT_4:9; :: thesis:
8161 = (67 * 121) + 54 ;
hence not 67 divides 8161 by NAT_4:9; :: thesis:
8161 = (71 * 114) + 67 ;
hence not 71 divides 8161 by NAT_4:9; :: thesis:
8161 = (73 * 111) + 58 ;
hence not 73 divides 8161 by NAT_4:9; :: thesis:
8161 = (79 * 103) + 24 ;
hence not 79 divides 8161 by NAT_4:9; :: thesis:
8161 = (83 * 98) + 27 ;
hence not 83 divides 8161 by NAT_4:9; :: thesis:
8161 = (89 * 91) + 62 ;
hence not 89 divides 8161 by NAT_4:9; :: thesis:

end;

then for n being Element of NAT st 1 < n & n * n <= 8161 & n is prime holds
not n divides 8161 by XPRIMET1:48;
hence 8161 is prime by NAT_4:14; :: thesis: