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.
Common factors of 10 and 63 are: 1.
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.
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 common factors of 54 and 63 are: 1, 3, and 9
The common factors of 36 and 63 are 1, 3 and 9