We divide 21510903 by 400
Let's see how many times 400 fits into 21510903.

Step 1:
The number 400 fits into 2 0 times, leaving a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Fetch the next digit (1) from the dividend, attach it to 2 and continue: 21 / 400

On to step 2:
If we divide 21 by 400, we get 0 and a remainder of 21.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 21 to get 21.
Append the next digit (5) from the dividend to 21 and continue with: 215 / 400

Moving on to step 3:
If we divide 215 by 400, we get 0 and a remainder of 215.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 215 leaves us with 215.
Append the next digit (1) from the dividend to 215 and continue with: 2151 / 400

Let's proceed to step 4:
When dividing 2151 by 400, we get 5 with a remainder of 151.
Use 5 as the next digit of our solution. 
Result so far: 5.0
Deduct 2000 from 2151 and we're left with 151.
Include the next digit (0) from the dividend after 151, then repeat: 1510 / 400

Moving on to step 5:
When dividing 1510 by 400, we get 3 with a remainder of 310.
Use 3 as the next digit of our solution. 
Result so far: 53.0
The remainder is 310 after subtracting 1200 from 1510.
Bring next digit (9) of the dividend behind the 310 and repeat the process: 3109 / 400

Let's proceed to step 6:
When dividing 3109 by 400, we get 7 with a remainder of 309.
Use 7 as the next digit of our solution. 
Result so far: 537.0
Subtracting 2800 from 3109 leaves us with 309.
Take the next digit (0) from the dividend and append it to 309, then repeat: 3090 / 400

Moving on to step 7:
3090 divided by 400 is 7 with a remainder of 290.
The number 7 becomes the next digit in our result. 
Result so far: 5377.0
If we take 2800 away from 3090, we end up with 290.
Fetch the next digit (3) from the dividend, attach it to 290 and continue: 2903 / 400

On to step 8:
When dividing 2903 by 400, we get 7 with a remainder of 103.
The number 7 becomes the next digit in our result. 
Result so far: 53777.0
Subtract 2800 from 2903 to get 103.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1030, and continue the process.

Going ahead to step 9:
If we divide 1030 by 400, we get 2 and a remainder of 230.
Use 2 as the next digit of our solution. 
Result so far: 53777.2
If we take 800 away from 1030, we end up with 230.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2300, and continue the process.

Step 10:
If we divide 2300 by 400, we get 5 and a remainder of 300.
Put 5 as the next digit of the answer. 
Result so far: 53777.25
The remainder is 300 after subtracting 2000 from 2300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3000, and continue the process.

On to step 11:
The number 400 fits into 3000 7 times, leaving a remainder of 200.
The next digit of our result is 7. 
Result so far: 53777.257
The remainder is 200 after subtracting 2800 from 3000.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Step 12:
The number 400 fits into 2000 5 times, leaving a remainder of 0.
Write down 5 as next digit of the result. 
Result so far: 53777.2575
The remainder is 0 after subtracting 2000 from 2000.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 13:
When dividing 0 by 400, we get 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 53777.2575
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Let's proceed to step 14:
When dividing 0 by 400, we get 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 53777.2575
Deduct 0 from 0 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

After the division, we end up with 53777.2575 and a remainder of 0.0.