81851 ÷ 5 = 16370 R1
Alright, let's work through the division of 81851 by 5 step by step.

Step 1:
5 goes into 8 1 times with a remainder of 3.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 5 from 8 to get 3.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 5

Step 2:
5 goes into 31 6 times with a remainder of 1.
Write down 6 as next digit of of the result. 
Result so far: 16
Subtract 30 from 31 to get 1.
Bring next digit (8) of the dividend behind the 1 and repeat the process: 18 / 5

Step 3:
5 goes into 18 3 times with a remainder of 3.
Write down 3 as next digit of of the result. 
Result so far: 163
Subtract 15 from 18 to get 3.
Bring next digit (5) of the dividend behind the 3 and repeat the process: 35 / 5

Step 4:
5 goes into 35 7 times with a remainder of 0.
Write down 7 as next digit of of the result. 
Result so far: 1637
Subtract 35 from 35 to get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 5

Step 5:
5 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 16370
Subtract 0 from 1 to get 1.

The final result is 16370 with a remainder of 1.