No, prime numbers do not have proper factors.
palindromes
It can be. 44 is a proper factor of 88, among other numbers.
97 is prime. Prime numbers don't have proper factors.
Prime numbers don't have proper factors.
Yes.
Complex numbers are a proper superset of real numbers. That is to say, real numbers are a proper subset of complex numbers.
Counting numbers are a proper subset of whole numbers which are the same as integers which are a proper subset of rational numbers.
No. Natural numbers are a proper subset of real numbers.
All numbers are factors (of their multiples).
MDCCCCXX or perhaps MCMXX. I think the first is more authentically Roman, but the second may be more commonly used today, and is shorter.
Prime numbers don't have proper factors.
Prime numbers don't have proper factors.
Prime numbers don't have proper factors.
Prime numbers don't have proper factors.
Prime numbers don't have proper factors.
Prime numbers don't have proper factors.