Respuesta :

sqdancefan
The given terms can be arranged in 3! = 6 ways. The other 5 are ...
  13 × 21 × 7
  7 × 13 × 21
  7 × 21 × 13
  21 × 7 × 13
  21 × 13 × 7
Any of these arrangements will give the same answer, 1,911.