839590 ÷ 21 
We want to divide 839590 by 21.

Let's proceed to step 1:
The number 21 fits into 8 0 times, leaving a remainder of 8.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Include the next digit (3) from the dividend after 8, then repeat: 83 / 21

Going ahead to step 2:
83 divided by 21 is 3 with a remainder of 20.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
If we subtract 63 from 83, we get 20.
Include the next digit (9) from the dividend after 20, then repeat: 209 / 21

Moving on to step 3:
If we divide 209 by 21, we get 9 and a remainder of 20.
Use 9 as the next digit of our solution. 
Result so far: 39.0
Subtracting 189 from 209 leaves us with 20.
Take the next digit (5) from the dividend and append it to 20, then repeat: 205 / 21

Advancing to step 4:
21 goes into 205 9 times with a remainder of 16.
The next digit of our result is 9. 
Result so far: 399.0
If we take 189 away from 205, we end up with 16.
Fetch the next digit (9) from the dividend, attach it to 16 and continue: 169 / 21

On to step 5:
When dividing 169 by 21, we get 8 with a remainder of 1.
The next digit of our result is 8. 
Result so far: 3998.0
Deduct 168 from 169 and we're left with 1.
Fetch the next digit (0) from the dividend, attach it to 1 and continue: 10 / 21

Let's proceed to step 6:
If we divide 10 by 21, we get 0 and a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 39980.0
Subtracting 0 from 10 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 7:
21 can be fit into 100 4 times, resulting in a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 39980.4
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 8:
If we divide 160 by 21, we get 7 and a remainder of 13.
The next digit of our result is 7. 
Result so far: 39980.47
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 9:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 39980.476
Subtracting 126 from 130 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 10:
21 goes into 40 1 times with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 39980.4761
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 11:
21 goes into 190 9 times with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 39980.47619
If we take 189 away from 190, we end up with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Moving on to step 12:
21 goes into 10 0 times with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 39980.47619
If we take 0 away from 10, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 13:
If we divide 100 by 21, we get 4 and a remainder of 16.
The next digit of our result is 4. 
Result so far: 39980.4761904
If we subtract 84 from 100, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 14:
160 divided by 21 is 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 39980.47619047
Deduct 147 from 160 and we're left with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

The final outcome is 39980.47619047, with a leftover of 1.3e-08.