We look at the division of 721521 by 51 
Let's see how many times 51 fits into 721521.

Step 1:
When dividing 7 by 51, we get 0 with a remainder of 7.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Include the next digit (2) from the dividend after 7, then repeat: 72 / 51

Moving on to step 2:
51 can be fit into 72 1 times, resulting in a remainder of 21.
Put 1 as the next digit of the answer. 
Result so far: 1.0
Subtract 51 from 72 to get 21.
Append the next digit (1) from the dividend to 21 and continue with: 211 / 51

Let's proceed to step 3:
51 goes into 211 4 times with a remainder of 7.
The number 4 becomes the next digit in our result. 
Result so far: 14.0
If we subtract 204 from 211, we get 7.
Grab the next digit (5) from the dividend, add it to 7, then carry on: 75 / 51

Step 4:
If we divide 75 by 51, we get 1 and a remainder of 24.
Record the quotient 1 as the next digit in the result. 
Result so far: 141.0
Subtract 51 from 75 to get 24.
Grab the next digit (2) from the dividend, add it to 24, then carry on: 242 / 51

On to step 5:
When dividing 242 by 51, we get 4 with a remainder of 38.
The number 4 becomes the next digit in our result. 
Result so far: 1414.0
If we subtract 204 from 242, we get 38.
Take the next digit (1) from the dividend and append it to 38, then repeat: 381 / 51

Let's proceed to step 6:
The number 51 fits into 381 7 times, leaving a remainder of 24.
The number 7 becomes the next digit in our result. 
Result so far: 14147.0
Deduct 357 from 381 and we're left with 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Advancing to step 7:
51 can be fit into 240 4 times, resulting in a remainder of 36.
Use 4 as the next digit of our solution. 
Result so far: 14147.4
If we subtract 204 from 240, we get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Step 8:
51 can be fit into 360 7 times, resulting in a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 14147.47
Deduct 357 from 360 and we're left with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Let's proceed to step 9:
The number 51 fits into 30 0 times, leaving a remainder of 30.
The next digit of our result is 0. 
Result so far: 14147.47
If we subtract 0 from 30, we get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Let's proceed to step 10:
If we divide 300 by 51, we get 5 and a remainder of 45.
The number 5 becomes the next digit in our result. 
Result so far: 14147.4705
Subtract 255 from 300 to get 45.
Since there are no more digits in the dividend, we add a zero to the remainder making it 450, and continue the process.

Moving on to step 11:
If we divide 450 by 51, we get 8 and a remainder of 42.
The next digit of our result is 8. 
Result so far: 14147.47058
If we take 408 away from 450, we end up with 42.
Since there are no more digits in the dividend, we add a zero to the remainder making it 420, and continue the process.

Let's proceed to step 12:
51 can be fit into 420 8 times, resulting in a remainder of 12.
The next digit of our result is 8. 
Result so far: 14147.470588
If we take 408 away from 420, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Our division results in 14147.470588 with a remaining 1.2e-06.