
theorem
  1979 is prime
proof
  now
    1979 = 2*989 + 1; hence not 2 divides 1979 by NAT_4:9;
    1979 = 3*659 + 2; hence not 3 divides 1979 by NAT_4:9;
    1979 = 5*395 + 4; hence not 5 divides 1979 by NAT_4:9;
    1979 = 7*282 + 5; hence not 7 divides 1979 by NAT_4:9;
    1979 = 11*179 + 10; hence not 11 divides 1979 by NAT_4:9;
    1979 = 13*152 + 3; hence not 13 divides 1979 by NAT_4:9;
    1979 = 17*116 + 7; hence not 17 divides 1979 by NAT_4:9;
    1979 = 19*104 + 3; hence not 19 divides 1979 by NAT_4:9;
    1979 = 23*86 + 1; hence not 23 divides 1979 by NAT_4:9;
    1979 = 29*68 + 7; hence not 29 divides 1979 by NAT_4:9;
    1979 = 31*63 + 26; hence not 31 divides 1979 by NAT_4:9;
    1979 = 37*53 + 18; hence not 37 divides 1979 by NAT_4:9;
    1979 = 41*48 + 11; hence not 41 divides 1979 by NAT_4:9;
    1979 = 43*46 + 1; hence not 43 divides 1979 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 1979 & n is prime
  holds not n divides 1979 by XPRIMET1:28;
  hence thesis by NAT_4:14;
end;
