#### Answer

$117=3\times3\times13$.

#### Work Step by Step

Since the sum of the digits of 117 is 9, 117 is divisible by 9, which means it is also divisible by 3. When we divide 117 by 3, we get 39. 39 is further divisible by 3 and results in 13. 13 is not divisible by any number except 1 and is therefore a prime number. Since 3, 3, and 13 are prime factors, the prime factorization of 117 is $3\times3\times13$.