Math Problem (Level 2) : Multiple of each number of digit (GG34)

According to the following example, the number of all digits of a certain integer is multiplied and this operation is repeated until the answer becomes the number of single digit.
Answer the following questions.

<Example>
327 → 3 × 2 × 7 = 42 → 4 × 2 = 8
73 → 7 × 3 = 21 → 2 × 1 = 2

(1) Find the final answer when 279 is operated.

(2) Find the number of the integer of double digit when it is operated, the final answer becomes 6.

Answer
(1) 2
(2) 13 pieces