Test for Divisibility by 3:
• A Number is divisible by 3 if the Sum of the Digits in the Number is divisible by 3
Sum of the Digits in 21: 2+1 = 3
3 is divisible by 3, 3/3 = 1
Therefore, 21 is divisible by 3
21/3 = 7
Test 21 for Divisibility by 3
The solution above and all other related solutions were provided by the Test for Divisibility by 3 Application.