How do you get 60 for 12345 as factors What is the name for that number?

To find the smallest number that has 1, 2, 3, 4 and 5 as factors, you're looking for the least common multiple, or LCM, of those numbers. You can find that by listing the multiples of each number but it's faster to combine their prime factors. You need two twos, a three and a five.

2 x 2 x 3 x 5 = 60