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

theorem Th26:
  m * n = p implies m = 1 & n = p or m = p & n = 1
  proof
    assume
A1: m*n = p;
    m divides m*n & n divides m*n;
    then (m = 1 or m = p) & (n = 1 or n = p) by A1,INT_2:def 4;
    hence thesis by A1;
  end;
