37221 ÷ 3 = 12407 R0
Let's divide 37221 by 3.

Step 1:
3 goes into 3 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 3 from 3 to get 0.
Bring next digit (7) of the dividend behind the 0 and repeat the process: 7 / 3

Step 2:
3 goes into 7 2 times with a remainder of 1.
Write down 2 as next digit of of the result. 
Result so far: 12
Subtract 6 from 7 to get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 3

Step 3:
3 goes into 12 4 times with a remainder of 0.
Write down 4 as next digit of of the result. 
Result so far: 124
Subtract 12 from 12 to get 0.
Bring next digit (2) of the dividend behind the 0 and repeat the process: 2 / 3

Step 4:
3 goes into 2 0 times with a remainder of 2.
Write down 0 as next digit of of the result. 
Result so far: 1240
Subtract 0 from 2 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 3

Step 5:
3 goes into 21 7 times with a remainder of 0.
Write down 7 as next digit of of the result. 
Result so far: 12407
Subtract 21 from 21 to get 0.

The final result is 12407 with a remainder of 0.