1 and 7.
The only common factor is 1.
21 and 35's highest common factor is seven.
The GCF is 7.
7
5
5
49. And35
140
The LCM is: 840
It is: 21/35 = 3/5 in its simplest form
The Greatest Common Factor (GCF) is: 5
The common factors of 21 and 51 are: 1 and 3