287451 ÷ 21 
We're looking to find how many times 21 goes into 287451.

On to step 1:
21 can be fit into 2 0 times, resulting in a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Grab the next digit (8) from the dividend, add it to 2, then carry on: 28 / 21

Advancing to step 2:
21 goes into 28 1 times with a remainder of 7.
Put 1 as the next digit of the answer. 
Result so far: 1.0
The remainder is 7 after subtracting 21 from 28.
Append the next digit (7) from the dividend to 7 and continue with: 77 / 21

Moving on to step 3:
21 can be fit into 77 3 times, resulting in a remainder of 14.
The next digit of our result is 3. 
Result so far: 13.0
If we take 63 away from 77, we end up with 14.
Grab the next digit (4) from the dividend, add it to 14, then carry on: 144 / 21

Let's proceed to step 4:
When dividing 144 by 21, we get 6 with a remainder of 18.
Record the quotient 6 as the next digit in the result. 
Result so far: 136.0
If we subtract 126 from 144, we get 18.
Include the next digit (5) from the dividend after 18, then repeat: 185 / 21

Advancing to step 5:
If we divide 185 by 21, we get 8 and a remainder of 17.
The number 8 becomes the next digit in our result. 
Result so far: 1368.0
Deduct 168 from 185 and we're left with 17.
Fetch the next digit (1) from the dividend, attach it to 17 and continue: 171 / 21

Moving on to step 6:
If we divide 171 by 21, we get 8 and a remainder of 3.
Record the quotient 8 as the next digit in the result. 
Result so far: 13688.0
If we subtract 168 from 171, we get 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 7:
30 divided by 21 is 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 13688.1
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 8:
90 divided by 21 is 4 with a remainder of 6.
The next digit of our result is 4. 
Result so far: 13688.14
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 9:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 13688.142
If we take 42 away from 60, we end up 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 10:
21 goes into 180 8 times with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 13688.1428
Subtract 168 from 180 to get 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 11:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 13688.14285
If we take 105 away from 120, we end up 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.

Step 12:
150 divided by 21 is 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 13688.142857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Step 13:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 13688.1428571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Step 14:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 13688.14285714
Subtract 84 from 90 to get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

The quotient of the division is 13688.14285714, and the remainder is 6e-09.