The greatest common factor of a prime number & a composite number is 1 if the composite number is not divisible by the prime number. 81(composite number) is not divisible by 29(prime number) so, gcf(29,81) = 1.
The greatest factor of any number is the number itself. The second greatest factor of any even number is half the number. The second greatest factor of any composite number is the number divided by its smallest prime factor. The second greatest factor of any prime number is 1.
This is a question that cannot be answered. First, 64 is not a prime number. Second, the greatest common factor is the factor that two or more numbers have in common. There is no greatest common factor of a single number, such as 64.