
theorem
  2143 is prime
proof
  now
    2143 = 2*1071 + 1; hence not 2 divides 2143 by NAT_4:9;
    2143 = 3*714 + 1; hence not 3 divides 2143 by NAT_4:9;
    2143 = 5*428 + 3; hence not 5 divides 2143 by NAT_4:9;
    2143 = 7*306 + 1; hence not 7 divides 2143 by NAT_4:9;
    2143 = 11*194 + 9; hence not 11 divides 2143 by NAT_4:9;
    2143 = 13*164 + 11; hence not 13 divides 2143 by NAT_4:9;
    2143 = 17*126 + 1; hence not 17 divides 2143 by NAT_4:9;
    2143 = 19*112 + 15; hence not 19 divides 2143 by NAT_4:9;
    2143 = 23*93 + 4; hence not 23 divides 2143 by NAT_4:9;
    2143 = 29*73 + 26; hence not 29 divides 2143 by NAT_4:9;
    2143 = 31*69 + 4; hence not 31 divides 2143 by NAT_4:9;
    2143 = 37*57 + 34; hence not 37 divides 2143 by NAT_4:9;
    2143 = 41*52 + 11; hence not 41 divides 2143 by NAT_4:9;
    2143 = 43*49 + 36; hence not 43 divides 2143 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 2143 & n is prime
  holds not n divides 2143 by XPRIMET1:28;
  hence thesis by NAT_4:14;
end;
