9 and 18
That happens when one of the numbers is a factor of the other.
A prime number
One is.
Any pair of prime numbers
Even numbers.
The least common factor of any set of numbers is 1.
1
yes
Yes, a pair of numbers can have fewer than two common factors. This only happens when the numbers are co-prime -- that is, when the numbers have only one common factor. In that case, the common factor is always 1.
The least common factor of any set of numbers is 1.
Only if the magnitudes of two numbers are the same.
Any consecutive even numbers.