It has degree 4, with 21 vertices and 42 edges.
It has girth 4, diameter 3 and radius 3.
Its symmetry group has 84 elements.
It is not bipartite.
It is Hamiltonian.
It is symmetric.
It is 1-arc-transitive.
Its distance-list is 1,4,8,8.
21-circulant(1,8) can be regarded as 7-cycle × K3