Which of the following number(s) are divisible by 3 :

1. 261

2. 777

3. 6657

According to the divisibility of 3, if the sum of the digits of the number is divisible by 3 then the number is divisible by 3.

1. 261 = 2 + 6 + 1 = 9. And 9 is divisible by 3

2. 777 = 7 + 7 + 7 = 21. And 21 is divisible by 3

3. 6657 = 6 + 6 + 5 + 7 = 24. And 24 is divisible by 3

Hence, all the three numbers, 261, 777 and 6657 are divisible by 3.