Though we do not know the greatest (known) prime number, there is no reason or proof that a larger one does not exist. So there is no greatest prime number any more than there is a greatest number.

A prime number is any number that only has one and itself as factors. By definition even numbers have a factor of two. Therefore the greatest and only even number that is prime is the number 2.

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.

The answer is 1. The smallest prime is 2 and the greatest prime (of however many digits) must be odd. The remainder of ANY odd number when divided by 2 must be 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.