Not necessarily.
Yes.
No.
Composite. All whole numbers ending in zero are composite.
If the GCF of two composite numbers is 1, they are co-prime or relatively prime.
Not necessarily.
25 and 36
8 and 16
Yes.
15 and 16
24, 25 and 26
8 and 16
8 and 16
No.
8 and 16, among others.
25 and 32