The LCM is 63.
126
315
You can have three common multiples, but only one can be least and that's 126. Others include 252 and 378.
The common multiples of 9 and 21 are 63, 126, 189 and so on.
The least common multiples of the number 6 and 9 is 3.
The only Least Common Multiple (LCM) for 7 9 14 is 126.
Any pair of numbers has an infinite set of common multiples. The lowest common multiple of 9 and 21 is 63 and the others are multiples of this, e.g. 63, 126, 189, 252, 315, ...
You need at least two numbers to compare multiples.
90 is the least common multiple of 9 and 10
lcm(4, 9) = 36 → the two least common multiples (ie the first two common multiples) of 4 and 9 are 36 and 72.
The common multiples of 9 and 16 are 144, 288, 432 and so on.
The Least Common Multiple of 9 and 15 is 45.