
theorem
  1021 is prime
proof
  now
    1021 = 2*510 + 1; hence not 2 divides 1021 by NAT_4:9;
    1021 = 3*340 + 1; hence not 3 divides 1021 by NAT_4:9;
    1021 = 5*204 + 1; hence not 5 divides 1021 by NAT_4:9;
    1021 = 7*145 + 6; hence not 7 divides 1021 by NAT_4:9;
    1021 = 11*92 + 9; hence not 11 divides 1021 by NAT_4:9;
    1021 = 13*78 + 7; hence not 13 divides 1021 by NAT_4:9;
    1021 = 17*60 + 1; hence not 17 divides 1021 by NAT_4:9;
    1021 = 19*53 + 14; hence not 19 divides 1021 by NAT_4:9;
    1021 = 23*44 + 9; hence not 23 divides 1021 by NAT_4:9;
    1021 = 29*35 + 6; hence not 29 divides 1021 by NAT_4:9;
    1021 = 31*32 + 29; hence not 31 divides 1021 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 1021 & n is prime
  holds not n divides 1021 by XPRIMET1:22;
  hence thesis by NAT_4:14;
end;
