51381 ÷ 4 = 12845 R1
Alright, let's work through the division of 51381 by 4 step by step.

Step 1:
4 goes into 5 1 times with a remainder of 1.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 4 from 5 to get 1.
Bring next digit (1) of the dividend behind the 1 and repeat the process: 11 / 4

Step 2:
4 goes into 11 2 times with a remainder of 3.
Write down 2 as next digit of of the result. 
Result so far: 12
Subtract 8 from 11 to get 3.
Bring next digit (3) of the dividend behind the 3 and repeat the process: 33 / 4

Step 3:
4 goes into 33 8 times with a remainder of 1.
Write down 8 as next digit of of the result. 
Result so far: 128
Subtract 32 from 33 to get 1.
Bring next digit (8) of the dividend behind the 1 and repeat the process: 18 / 4

Step 4:
4 goes into 18 4 times with a remainder of 2.
Write down 4 as next digit of of the result. 
Result so far: 1284
Subtract 16 from 18 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 4

Step 5:
4 goes into 21 5 times with a remainder of 1.
Write down 5 as next digit of of the result. 
Result so far: 12845
Subtract 20 from 21 to get 1.

The final result is 12845 with a remainder of 1.