## Where is it?

Putting the permutations obtained by the 5 digits in ascending order:
1xxxx => P4 = 4! = 24
2xxxx => P4 = 4! = 24
3xxxx => P4 = 4! = 24
41xxx => P3 = 3! = 6
42xxx => P3 = 3! = 6
431xx => P2 = 2! = 2
432xx => P2 = 2! = 2
4351x => P1 = 1! = 1

Summing them all:
24+24+24+6+6+2+2+1 = 89

So the number 43521 is at position 89 + 1 = 90.
Answer: The number 43521 is in 90º position.

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