Question 4308
  Yes, since 3 is a divisor.

 An integer is a multiple of 3 if and only if the sum of all its
 digits is a divisor of 3.

  In fact , there is not necessary to add up all the digits, because
  we can consider all mltiples of 3 as zeros and ignore them.

 13346355645635645364562354623567
 (ignore 3, 6) -->14554554545254257
 (ignore 45,54,57) -->15522
 (ignore 15) -->522
  (sum of all digits = 9) --> the origin huge number is a multiple of 3.

 After more practice, you can check if a given integer is equal to
 0 mod 3 faster.)


  If you want to test if it is a multiple of 9.
  
 (Ignore 45, 63,36 and 54)--> 1334556635662354623567
 (Ignore 45, 63,36, 54 )--> 1335656623623567
 (Ignore a pair of (3 ,6) , (4,5) & (2,7)) --> 155625
 (Ignore 162) -> 555 --> sum = 15 --> sum= 1+5= 6 
 --> multiple of 3 (but not 9)

 Kenny