
theorem
  2153 is prime
proof
  now
    2153 = 2*1076 + 1; hence not 2 divides 2153 by NAT_4:9;
    2153 = 3*717 + 2; hence not 3 divides 2153 by NAT_4:9;
    2153 = 5*430 + 3; hence not 5 divides 2153 by NAT_4:9;
    2153 = 7*307 + 4; hence not 7 divides 2153 by NAT_4:9;
    2153 = 11*195 + 8; hence not 11 divides 2153 by NAT_4:9;
    2153 = 13*165 + 8; hence not 13 divides 2153 by NAT_4:9;
    2153 = 17*126 + 11; hence not 17 divides 2153 by NAT_4:9;
    2153 = 19*113 + 6; hence not 19 divides 2153 by NAT_4:9;
    2153 = 23*93 + 14; hence not 23 divides 2153 by NAT_4:9;
    2153 = 29*74 + 7; hence not 29 divides 2153 by NAT_4:9;
    2153 = 31*69 + 14; hence not 31 divides 2153 by NAT_4:9;
    2153 = 37*58 + 7; hence not 37 divides 2153 by NAT_4:9;
    2153 = 41*52 + 21; hence not 41 divides 2153 by NAT_4:9;
    2153 = 43*50 + 3; hence not 43 divides 2153 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 2153 & n is prime
  holds not n divides 2153 by XPRIMET1:28;
  hence thesis by NAT_4:14;
end;
