393419 ÷ 21 
We're looking to find how many times 21 goes into 393419.

Advancing to step 1:
21 goes into 3 0 times with a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Fetch the next digit (9) from the dividend, attach it to 3 and continue: 39 / 21

Moving on to step 2:
21 can be fit into 39 1 times, resulting in a remainder of 18.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
If we take 21 away from 39, we end up with 18.
Bring next digit (3) of the dividend behind the 18 and repeat the process: 183 / 21

Going ahead to step 3:
21 can be fit into 183 8 times, resulting in a remainder of 15.
The next digit of our result is 8. 
Result so far: 18.0
Deduct 168 from 183 and we're left with 15.
Fetch the next digit (4) from the dividend, attach it to 15 and continue: 154 / 21

Step 4:
154 divided by 21 is 7 with a remainder of 7.
Record the quotient 7 as the next digit in the result. 
Result so far: 187.0
Subtracting 147 from 154 leaves us with 7.
Append the next digit (1) from the dividend to 7 and continue with: 71 / 21

Let's proceed to step 5:
71 divided by 21 is 3 with a remainder of 8.
Record the quotient 3 as the next digit in the result. 
Result so far: 1873.0
The remainder is 8 after subtracting 63 from 71.
Bring next digit (9) of the dividend behind the 8 and repeat the process: 89 / 21

On to step 6:
The number 21 fits into 89 4 times, leaving a remainder of 5.
Write down 4 as next digit of the result. 
Result so far: 18734.0
The remainder is 5 after subtracting 84 from 89.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Step 7:
21 goes into 50 2 times with a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 18734.2
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 8:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 18734.23
If we subtract 63 from 80, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Advancing to step 9:
170 divided by 21 is 8 with a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 18734.238
Subtract 168 from 170 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 10:
The number 21 fits into 20 0 times, leaving a remainder of 20.
Record the quotient 0 as the next digit in the result. 
Result so far: 18734.238
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 11:
21 goes into 200 9 times with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 18734.23809
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Moving on to step 12:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 18734.238095
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 13:
21 goes into 50 2 times with a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 18734.2380952
Deduct 42 from 50 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Let's proceed to step 14:
21 can be fit into 80 3 times, resulting in a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 18734.23809523
Deduct 63 from 80 and we're left with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Our division results in 18734.23809523 with a remaining 1.7e-08.