When dealing with several numbers, the lowest(or least) common multiple can be applied consecutively, i.e.
lcm( 4,9,13)
=lcm(4, lcm(9,13)) (or lcm(lcm(4,9), 13)
(i.e. find the lowest common of any 2 numbers, and then find the lowest common multiple of the result and the remaining number)
lcm(9,13) = 9 x 13 = 117
(13 is a prime, so no chance of common factors)
http://statsfiddle.info/Primes/LowestCommonMultiple/9?number2=13
lcm(117,4) = 468
Again, there are no common factors
http://statsfiddle.info/Primes/LowestCommonMultiple/117?number2=4
i.e. lcm(4, 9,13) = 468
In your example, all 3 numbers are co-prime, meaning there are no common factors at all.