We're dividing 120651 by 21 
We're looking to find how many times 21 goes into 120651.

Going ahead to step 1:
When dividing 1 by 21, we get 0 with a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Grab the next digit (2) from the dividend, add it to 1, then carry on: 12 / 21

Advancing to step 2:
If we divide 12 by 21, we get 0 and a remainder of 12.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 12, we end up with 12.
Bring next digit (0) of the dividend behind the 12 and repeat the process: 120 / 21

On to step 3:
If we divide 120 by 21, we get 5 and a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 5.0
Deduct 105 from 120 and we're left with 15.
Append the next digit (6) from the dividend to 15 and continue with: 156 / 21

Step 4:
When dividing 156 by 21, we get 7 with a remainder of 9.
The next digit of our result is 7. 
Result so far: 57.0
The remainder is 9 after subtracting 147 from 156.
Include the next digit (5) from the dividend after 9, then repeat: 95 / 21

Going ahead to step 5:
95 divided by 21 is 4 with a remainder of 11.
Record the quotient 4 as the next digit in the result. 
Result so far: 574.0
Deduct 84 from 95 and we're left with 11.
Take the next digit (1) from the dividend and append it to 11, then repeat: 111 / 21

Advancing to step 6:
The number 21 fits into 111 5 times, leaving a remainder of 6.
Write down 5 as next digit of the result. 
Result so far: 5745.0
The remainder is 6 after subtracting 105 from 111.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 7:
60 divided by 21 is 2 with a remainder of 18.
The next digit of our result is 2. 
Result so far: 5745.2
Subtracting 42 from 60 leaves us with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Advancing to step 8:
180 divided by 21 is 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 5745.28
Deduct 168 from 180 and we're left 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.

Moving on to step 9:
If we divide 120 by 21, we get 5 and a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 5745.285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 10:
If we divide 150 by 21, we get 7 and a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 5745.2857
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 11:
21 goes into 30 1 times with a remainder of 9.
The next digit of our result is 1. 
Result so far: 5745.28571
Subtracting 21 from 30 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 12:
If we divide 90 by 21, we get 4 and a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 5745.285714
Deduct 84 from 90 and we're left with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 13:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 5745.2857142
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 5745.28571428
If we take 168 away from 180, 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.

After the division, we end up with 5745.28571428 and a remainder of 1.2e-08.