21405142 ÷ 15 
We want to divide 21405142 by 15.

Going ahead to step 1:
If we divide 2 by 15, we get 0 and a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 2 and we're left with 2.
Append the next digit (1) from the dividend to 2 and continue with: 21 / 15

Step 2:
When dividing 21 by 15, we get 1 with a remainder of 6.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtract 15 from 21 to get 6.
Bring next digit (4) of the dividend behind the 6 and repeat the process: 64 / 15

Moving on to step 3:
If we divide 64 by 15, we get 4 and a remainder of 4.
The next digit of our result is 4. 
Result so far: 14.0
Subtracting 60 from 64 leaves us with 4.
Include the next digit (0) from the dividend after 4, then repeat: 40 / 15

On to step 4:
15 can be fit into 40 2 times, resulting in a remainder of 10.
Use 2 as the next digit of our solution. 
Result so far: 142.0
If we take 30 away from 40, we end up with 10.
Bring next digit (5) of the dividend behind the 10 and repeat the process: 105 / 15

Step 5:
When dividing 105 by 15, we get 7 with a remainder of 0.
Write down 7 as next digit of the result. 
Result so far: 1427.0
If we subtract 105 from 105, we get 0.
Grab the next digit (1) from the dividend, add it to 0, then carry on: 1 / 15

Moving on to step 6:
15 can be fit into 1 0 times, resulting in a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 14270.0
Subtract 0 from 1 to get 1.
Grab the next digit (4) from the dividend, add it to 1, then carry on: 14 / 15

Let's proceed to step 7:
15 can be fit into 14 0 times, resulting in a remainder of 14.
Record the quotient 0 as the next digit in the result. 
Result so far: 142700.0
Deduct 0 from 14 and we're left with 14.
Take the next digit (2) from the dividend and append it to 14, then repeat: 142 / 15

On to step 8:
When dividing 142 by 15, we get 9 with a remainder of 7.
Record the quotient 9 as the next digit in the result. 
Result so far: 1427009.0
Deduct 135 from 142 and we're left with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Let's proceed to step 9:
15 can be fit into 70 4 times, resulting in a remainder of 10.
Use 4 as the next digit of our solution. 
Result so far: 1427009.4
The remainder is 10 after subtracting 60 from 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 10:
15 can be fit into 100 6 times, resulting in a remainder of 10.
Write down 6 as next digit of the result. 
Result so far: 1427009.46
If we subtract 90 from 100, we get 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 11:
The number 15 fits into 100 6 times, leaving a remainder of 10.
Put 6 as the next digit of the answer. 
Result so far: 1427009.466
Subtract 90 from 100 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Our division results in 1427009.466 with a remaining 0.001.