Unfortunately, this is impossible. On Subway Surfers, the best score of 2,147,483,647 points cannot be beaten. This can be explained quite simply by the game's operating system, which, although it seems infinite, has its limits.
This is a list of times I used to calculate the time for 1M in different multipliers: Multiplier 1: 7 hours 19 minutes 19 seconds. Multiplier 2: 3 hours 40 minutes 55 seconds. Multiplier 3: 2 hours 27 minutes 23 seconds.