
theorem
  907 is prime
proof
  now
    907 = 2*453 + 1; hence not 2 divides 907 by NAT_4:9;
    907 = 3*302 + 1; hence not 3 divides 907 by NAT_4:9;
    907 = 5*181 + 2; hence not 5 divides 907 by NAT_4:9;
    907 = 7*129 + 4; hence not 7 divides 907 by NAT_4:9;
    907 = 11*82 + 5; hence not 11 divides 907 by NAT_4:9;
    907 = 13*69 + 10; hence not 13 divides 907 by NAT_4:9;
    907 = 17*53 + 6; hence not 17 divides 907 by NAT_4:9;
    907 = 19*47 + 14; hence not 19 divides 907 by NAT_4:9;
    907 = 23*39 + 10; hence not 23 divides 907 by NAT_4:9;
    907 = 29*31 + 8; hence not 29 divides 907 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 907 & n is prime
  holds not n divides 907 by XPRIMET1:20;
  hence thesis by NAT_4:14;
