now :: thesis: ( not 2 divides 2153 & not 3 divides 2153 & not 5 divides 2153 & not 7 divides 2153 & not 11 divides 2153 & not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )

2153 = (2 * 1076) + 1 ;
hence not 2 divides 2153 by NAT_4:9; :: thesis: ( not 3 divides 2153 & not 5 divides 2153 & not 7 divides 2153 & not 11 divides 2153 & not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (3 * 717) + 2 ;
hence not 3 divides 2153 by NAT_4:9; :: thesis: ( not 5 divides 2153 & not 7 divides 2153 & not 11 divides 2153 & not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (5 * 430) + 3 ;
hence not 5 divides 2153 by NAT_4:9; :: thesis: ( not 7 divides 2153 & not 11 divides 2153 & not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (7 * 307) + 4 ;
hence not 7 divides 2153 by NAT_4:9; :: thesis: ( not 11 divides 2153 & not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (11 * 195) + 8 ;
hence not 11 divides 2153 by NAT_4:9; :: thesis: ( not 13 divides 2153 & not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (13 * 165) + 8 ;
hence not 13 divides 2153 by NAT_4:9; :: thesis: ( not 17 divides 2153 & not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (17 * 126) + 11 ;
hence not 17 divides 2153 by NAT_4:9; :: thesis: ( not 19 divides 2153 & not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (19 * 113) + 6 ;
hence not 19 divides 2153 by NAT_4:9; :: thesis: ( not 23 divides 2153 & not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (23 * 93) + 14 ;
hence not 23 divides 2153 by NAT_4:9; :: thesis: ( not 29 divides 2153 & not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (29 * 74) + 7 ;
hence not 29 divides 2153 by NAT_4:9; :: thesis: ( not 31 divides 2153 & not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (31 * 69) + 14 ;
hence not 31 divides 2153 by NAT_4:9; :: thesis: ( not 37 divides 2153 & not 41 divides 2153 & not 43 divides 2153 )
2153 = (37 * 58) + 7 ;
hence not 37 divides 2153 by NAT_4:9; :: thesis: ( not 41 divides 2153 & not 43 divides 2153 )
2153 = (41 * 52) + 21 ;
hence not 41 divides 2153 by NAT_4:9; :: thesis: not 43 divides 2153
2153 = (43 * 50) + 3 ;
hence not 43 divides 2153 by NAT_4:9; :: thesis: verum

end;

then for n being Element of NAT st 1 < n & n * n <= 2153 & n is prime holds
not n divides 2153 by XPRIMET1:28;
hence 2153 is prime by NAT_4:14; :: thesis: verum