When I get up, I will remember my old dream and make a number.

2 173。 According to the description of the riddle, it can be inferred that the riddle is a four-digit number. According to the key word in the prompt, we can understand "sleeping over old dreams" as "recalling the past". This means that numbers are related to memory. After dividing and arranging the words in the puzzle, you can get "new ideas and old dreams", and then divide the words to get "2 173". So the answer is 2 173.