reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r,s for Real;
reserve p,p1,p2,p3 for Prime;
reserve z for Complex;

theorem
  n is a_product_of_two_primes implies
  for a,b st a <> 1 & b <> 1 & n = a*b holds a is prime & b is prime
  by NUMBER07:59;
