153459 divided by 21 
We're looking to find how many times 21 goes into 153459.

Advancing to step 1:
21 can be fit into 1 0 times, resulting in a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Append the next digit (5) from the dividend to 1 and continue with: 15 / 21

On to step 2:
21 goes into 15 0 times with a remainder of 15.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 15, we get 15.
Fetch the next digit (3) from the dividend, attach it to 15 and continue: 153 / 21

On to step 3:
153 divided by 21 is 7 with a remainder of 6.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
If we take 147 away from 153, we end up with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 21

Let's proceed to step 4:
21 can be fit into 64 3 times, resulting in a remainder of 1.
The next digit of our result is 3. 
Result so far: 73.0
The remainder is 1 after subtracting 63 from 64.
Fetch the next digit (5) from the dividend, attach it to 1 and continue: 15 / 21

On to step 5:
When dividing 15 by 21, we get 0 with a remainder of 15.
The next digit of our result is 0. 
Result so far: 730.0
Subtracting 0 from 15 leaves us with 15.
Bring next digit (9) of the dividend behind the 15 and repeat the process: 159 / 21

Let's proceed to step 6:
If we divide 159 by 21, we get 7 and a remainder of 12.
Write down 7 as next digit of the result. 
Result so far: 7307.0
Subtracting 147 from 159 leaves us 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.

Advancing to step 7:
120 divided by 21 is 5 with a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 7307.5
Subtract 105 from 120 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

On to step 8:
If we divide 150 by 21, we get 7 and a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 7307.57
If we take 147 away from 150, we end up 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.

On to step 9:
If we divide 30 by 21, we get 1 and a remainder of 9.
The next digit of our result is 1. 
Result so far: 7307.571
If we take 21 away from 30, we end up 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.

Step 10:
90 divided by 21 is 4 with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 7307.5714
If we take 84 away from 90, we end up 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.

Moving on to step 11:
60 divided by 21 is 2 with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 7307.57142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Let's proceed to step 12:
If we divide 180 by 21, we get 8 and a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 7307.571428
The remainder is 12 after subtracting 168 from 180.
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 13:
21 can be fit into 120 5 times, resulting in a remainder of 15.
The number 5 becomes the next digit in our result. 
Result so far: 7307.5714285
Subtracting 105 from 120 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 14:
If we divide 150 by 21, we get 7 and a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 7307.57142857
Subtracting 147 from 150 leaves us 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.

The final outcome is 7307.57142857, with a leftover of 3e-09.