Two common multiples of 21 and 15 are 105 and 315.
There are an infinite number of common multiples of 21 and 15 .The smallest two of them are 105 and 210 . A couple of others are 1,890 and 453,705 .
105 and 210
There is an infinite number of common multiples for 21 and 15. A common multiple of any two or more numbers is any number into which each of two or more numbers can be divided evenly (zero remainder).
105
The least common multiple or LMC of 15 and 21 is 105!!!
105, 210
They are infinite but the lowest common multiple is 105
315
21 and 28
You need at least two numbers to find a common multiple. Multiples of 21 in that range include 21, 42, 63 and 84
LCM of 21 & 49 is 147, so all multiples of 147 are common multiples of 21 & 49.