Short answer: There are none.
There is neither a greatest common factor nor common factors of a single number, such as 54, because there cannot be any form of common factor without two or more numbers to compare. Common factors are factors that the numbers being compared have in common. The greatest common factor is the largest factor that all the numbers being compared have in common. Thus, since there are not two or more numbers to compare, there are neither common factors nor a greatest common factor.
Examples:
The common factors of 4 and 54 are 1 and 2; the greatest common factors is 2.
The common factors of 18 and 54 are 1, 2, 3, 6, 9, and 18; the greatest common factor is 18.
The common factors of 32 and 54 are: 1 and 2
The common factors of 54 and 63 are: 1, 3, and 9
Since 18 is a factor of 54, all of its factors are common.
The common factors of 126 and 54 are: 1, 2, 3, 6, 9, and 18
The common factors of 42 and 54 are: 1, 2, 3, and 61, 2, 3 and 6.
Common factors of 54 and 22 are: 1 and 2.
The common factors of 32 and 54 are: 1 and 2
The common factors of 54 and 75 are 1 and 3.
Since 54 is a factor of 108, all of 54's factors are common and the GCF is 54 itself.
The common factors of 54 and 63 are: 1, 3, and 9
The common factors of 45 and 54 are: 1, 3, and 9
Since 18 is a factor of 54, all of its factors are common.
The common factors of 28 and 54 are: 1, 2
The common factors of 6 and 54 are: 1, 2, 3, and 6
The common factors of 54 and 276 are 1, 2, 3, and 6
Since 18 is a factor of 54, all of its factors are common.
The common factors of 12 and 54 are 1, 2, 3, and 6.