A family purchases 18 paintings to be hung on 6 walls in their place of residence. No two paintings can be hung on the same wall, and because there are more paintings than the target walls, the family will store the rest of the paintings in a storage space. After a few months, the paintings that are stored in the storage will be swapped with the paintings that are hung on the walls now. (Hint: ordering of the paintings on the walls matters). In how many different ways can 6 paintings be placed on the walls? (If your answer is too large, enter it without using any comma. The software will automatically insert the comma)