[4] It lies 2 degrees south of Sigma Leonis and is a member of the Herschel 400 Catalogue.

[5] NGC 3640 is an elliptical galaxy with a highly disturbed stellar component.

A dust lane is observed along the minor-axis, spanning 30 arcseconds in a north-south direction.

[8] In the centre of NGC 3640 lies a supermassive black hole whose mass is estimated to be roughly 100 million (107.99 ± 0.39) M☉ based on the Sérsic profile.

The group belongs to the Leo II groups, a large collection of galaxies belonging to the Virgo Supercluster scattered across 30 million light years of space west of the Virgo Cluster.