OK, so you want to get in to the party.
The door is being guarded by an elephant, who will trample any visitor who gives the wrong answer.
A polar bear comes up to the door. The elephant says, "1", and the polar bear replies "14", and is admitted.
Then a horned lark flies up to the door. The elephant says, "2". The lark twitters back "14" and is trampled.
Next up is a cat. The cat saunters up to the door, and the elephant says "2". The cat replies "10" and is admittted.
An emperor penguin waddles up to the door. The elephant says "3", and the penguin replies "19" (and is admitted).
Finally a massive tortoise, which has flown in specially from the Galapagos Islands just to attend this party, walks (very slowly) up to the door. The door-keeping elephant says "4" and the tortoise replies (very slowly) "Six" (deep breath, long pause) "teen". The tortoise is admitted to the party.
Now it's your turn. The elephant says "5"; what do you reply?