Just 1.
The factors of 43 are 1 and 43. For them to be common, they need to be compared to another set of factors.
43 is a prime number because it has exactly two factors, 1 and 43. 33 and 63 each have 3 as a factor as well as 1 and themselves, so they are composite numbers.
Common factors of 10 and 63 are: 1.
The common factors of 28 and 63 are: 1 and 7
The common factors of 30 and 63 are 1 and 3.
The common factors of 15 and 63 are: 1 and 3
The common factors of 63 and 91 are 1 and 7.
The common factors of 21 and 63 are 1, 3, 7, and 21
43 is a prime number so the common factors of 43 and 42 are 1
The factors of 43 are 1 and 43. For them to be common, they need to be compared to another set of factors.
The factors of 63 are 1, 3, 7, 9, 21 and 63. For them to be common, they need to be compared to another set of factors.
The common factors of 54 and 63 are: 1, 3, and 9