
theorem
  1871 is prime
proof
  now
    1871 = 2*935 + 1; hence not 2 divides 1871 by NAT_4:9;
    1871 = 3*623 + 2; hence not 3 divides 1871 by NAT_4:9;
    1871 = 5*374 + 1; hence not 5 divides 1871 by NAT_4:9;
    1871 = 7*267 + 2; hence not 7 divides 1871 by NAT_4:9;
    1871 = 11*170 + 1; hence not 11 divides 1871 by NAT_4:9;
    1871 = 13*143 + 12; hence not 13 divides 1871 by NAT_4:9;
    1871 = 17*110 + 1; hence not 17 divides 1871 by NAT_4:9;
    1871 = 19*98 + 9; hence not 19 divides 1871 by NAT_4:9;
    1871 = 23*81 + 8; hence not 23 divides 1871 by NAT_4:9;
    1871 = 29*64 + 15; hence not 29 divides 1871 by NAT_4:9;
    1871 = 31*60 + 11; hence not 31 divides 1871 by NAT_4:9;
    1871 = 37*50 + 21; hence not 37 divides 1871 by NAT_4:9;
    1871 = 41*45 + 26; hence not 41 divides 1871 by NAT_4:9;
    1871 = 43*43 + 22; hence not 43 divides 1871 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 1871 & n is prime
  holds not n divides 1871 by XPRIMET1:28;
  hence thesis by NAT_4:14;
end;
