
theorem
  3989 is prime
proof
  now
    3989 = 2*1994 + 1; hence not 2 divides 3989 by NAT_4:9;
    3989 = 3*1329 + 2; hence not 3 divides 3989 by NAT_4:9;
    3989 = 5*797 + 4; hence not 5 divides 3989 by NAT_4:9;
    3989 = 7*569 + 6; hence not 7 divides 3989 by NAT_4:9;
    3989 = 11*362 + 7; hence not 11 divides 3989 by NAT_4:9;
    3989 = 13*306 + 11; hence not 13 divides 3989 by NAT_4:9;
    3989 = 17*234 + 11; hence not 17 divides 3989 by NAT_4:9;
    3989 = 19*209 + 18; hence not 19 divides 3989 by NAT_4:9;
    3989 = 23*173 + 10; hence not 23 divides 3989 by NAT_4:9;
    3989 = 29*137 + 16; hence not 29 divides 3989 by NAT_4:9;
    3989 = 31*128 + 21; hence not 31 divides 3989 by NAT_4:9;
    3989 = 37*107 + 30; hence not 37 divides 3989 by NAT_4:9;
    3989 = 41*97 + 12; hence not 41 divides 3989 by NAT_4:9;
    3989 = 43*92 + 33; hence not 43 divides 3989 by NAT_4:9;
    3989 = 47*84 + 41; hence not 47 divides 3989 by NAT_4:9;
    3989 = 53*75 + 14; hence not 53 divides 3989 by NAT_4:9;
    3989 = 59*67 + 36; hence not 59 divides 3989 by NAT_4:9;
    3989 = 61*65 + 24; hence not 61 divides 3989 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 3989 & n is prime
  holds not n divides 3989 by XPRIMET1:36;
  hence thesis by NAT_4:14;
end;
