Why is 3 333 333 is not divisible by 9?

A number is divisible by 9 if the sum of its digits is divisible by 9. For 3,333,333, the sum of the digits is 3 + 3 + 3 + 3 + 3 + 3 + 3 = 21. Since 21 is not divisible by 9 (21 divided by 9 equals 2 with a remainder of 3), 3,333,333 is also not divisible by 9.