Is 703 composite

Answer 1

703 can be written as 19x 37. This is a hard number to know for sure is not prime. Keep in mind that you only need to check possible factors up to the square root of 703 which is about 26.
You can skip many factors such as 2 for example since the number is odd.
Skip 3 since the sum of the digits is 10 which is not a multiple of 3.
You will get all the way up to 19 before you find one factor. The good news is once you divide by 19, you get the other factor for free!