390021 ÷ 28 
We want to figure out the number of times 390021 can be divided by 28.

Step 1:
The number 28 fits into 3 0 times, leaving a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 28

Advancing to step 2:
39 divided by 28 is 1 with a remainder of 11.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtracting 28 from 39 leaves us with 11.
Grab the next digit (0) from the dividend, add it to 11, then carry on: 110 / 28

Let's proceed to step 3:
110 divided by 28 is 3 with a remainder of 26.
The next digit of our result is 3. 
Result so far: 13.0
The remainder is 26 after subtracting 84 from 110.
Grab the next digit (0) from the dividend, add it to 26, then carry on: 260 / 28

Let's proceed to step 4:
If we divide 260 by 28, we get 9 and a remainder of 8.
Write down 9 as next digit of the result. 
Result so far: 139.0
If we take 252 away from 260, we end up with 8.
Grab the next digit (2) from the dividend, add it to 8, then carry on: 82 / 28

On to step 5:
28 can be fit into 82 2 times, resulting in a remainder of 26.
Put 2 as the next digit of the answer. 
Result so far: 1392.0
If we subtract 56 from 82, we get 26.
Grab the next digit (1) from the dividend, add it to 26, then carry on: 261 / 28

On to step 6:
If we divide 261 by 28, we get 9 and a remainder of 9.
Put 9 as the next digit of the answer. 
Result so far: 13929.0
The remainder is 9 after subtracting 252 from 261.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 7:
The number 28 fits into 90 3 times, leaving a remainder of 6.
Put 3 as the next digit of the answer. 
Result so far: 13929.3
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.

Step 8:
60 divided by 28 is 2 with a remainder of 4.
Write down 2 as next digit of the result. 
Result so far: 13929.32
The remainder is 4 after subtracting 56 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Step 9:
28 goes into 40 1 times with a remainder of 12.
Put 1 as the next digit of the answer. 
Result so far: 13929.321
Subtracting 28 from 40 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 10:
The number 28 fits into 120 4 times, leaving a remainder of 8.
Write down 4 as next digit of the result. 
Result so far: 13929.3214
If we subtract 112 from 120, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 11:
80 divided by 28 is 2 with a remainder of 24.
Put 2 as the next digit of the answer. 
Result so far: 13929.32142
Deduct 56 from 80 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.

Moving on to step 12:
28 can be fit into 240 8 times, resulting in a remainder of 16.
Use 8 as the next digit of our solution. 
Result so far: 13929.321428
If we subtract 224 from 240, 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.

Going ahead to step 13:
28 can be fit into 160 5 times, resulting in a remainder of 20.
The next digit of our result is 5. 
Result so far: 13929.3214285
If we take 140 away from 160, 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 14:
When dividing 200 by 28, we get 7 with a remainder of 4.
Record the quotient 7 as the next digit in the result. 
Result so far: 13929.32142857
If we subtract 196 from 200, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

After the division, we end up with 13929.32142857 and a remainder of 4e-09.