20 is even so all multiples of 20 must be even. 1 is not even.
Multiples of what???For example, to get multiples of 20, just start with 20 and add 20 at a time: 20, 40, 60, ...
The numbers are: 1 and 20
The only multiples of 2 are 1 and 2 because it's a prime number, but if you meant first 2 multiples of 20 then it's also 1 and 2.
Multiples of 1 include 1, 2 and 3. For them to be common, they need to be compared to another set of multiples.
20,4,60,80,100
There are two which are 1*10 = 10 and 2*10 = 20
21
20 of them.
20, 40, 60, 80, 100.
To find the multiples of any number, multiply it by successive counting numbers.
All the multiples of 20 cannot be listed since they are infinite in number. They start 20, 40, 60, 80, 100, ...
Since 10 is a factor of 20, all multiples of 20 are multiples of 10. This is also true of 1, 2, 4 and 5.