51903 ÷ 4 = 12975 R3
Let's divide 51903 by 4.

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 (9) of the dividend behind the 3 and repeat the process: 39 / 4

Step 3:
4 goes into 39 9 times with a remainder of 3.
Write down 9 as next digit of of the result. 
Result so far: 129
Subtract 36 from 39 to get 3.
Bring next digit (0) of the dividend behind the 3 and repeat the process: 30 / 4

Step 4:
4 goes into 30 7 times with a remainder of 2.
Write down 7 as next digit of of the result. 
Result so far: 1297
Subtract 28 from 30 to get 2.
Bring next digit (3) of the dividend behind the 2 and repeat the process: 23 / 4

Step 5:
4 goes into 23 5 times with a remainder of 3.
Write down 5 as next digit of of the result. 
Result so far: 12975
Subtract 20 from 23 to get 3.

The final result is 12975 with a remainder of 3.