21515 ÷ 2 = 10757 R1
Let's divide 21515 by 2.

Step 1:
2 goes into 2 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 2 from 2 to get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 2

Step 2:
2 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 10
Subtract 0 from 1 to get 1.
Bring next digit (5) of the dividend behind the 1 and repeat the process: 15 / 2

Step 3:
2 goes into 15 7 times with a remainder of 1.
Write down 7 as next digit of of the result. 
Result so far: 107
Subtract 14 from 15 to get 1.
Bring next digit (1) of the dividend behind the 1 and repeat the process: 11 / 2

Step 4:
2 goes into 11 5 times with a remainder of 1.
Write down 5 as next digit of of the result. 
Result so far: 1075
Subtract 10 from 11 to get 1.
Bring next digit (5) of the dividend behind the 1 and repeat the process: 15 / 2

Step 5:
2 goes into 15 7 times with a remainder of 1.
Write down 7 as next digit of of the result. 
Result so far: 10757
Subtract 14 from 15 to get 1.

The final result is 10757 with a remainder of 1.