Its V–I color index of 0.77 is notably lower than that of a Jovian D-type asteroid, which is the dominant spectral type among the Jupiter trojans (also see table below).

[17] The first rotation period of 7.675±0.019 hours with a brightness variation of 0.18±0.01 was reported by Stefano Mottola, who observed Mentor in February 1993, using the former ESO 1-metre telescope at the La Silla Observatory in Chile (U=3-).

Follow-up observations by Mottola at the Calar Alto Observatory in July 1998 gave a refined period of 7.700±0.019 hours and an amplitude of 0.15±0.01 magnitude (U=3).

[18][19][20] Additional period determinations by Laurent Bernasconi (7.699 h) Federico Manzini (>6 h) and René Roy (7.727 and 7.6 h) were made between 2006 and 2010, and reported at Behrend's website.

[22] Follow-up observations by Daniel Coley and Robert Stephens at GMARS (G79) in 2010, and the Center for Solar System Studies during 2013–2017, measured four well-defined periods including 7.702±0.002 and 7.730±0.001 hours with a brightness amplitude of 0.46 and 0.21 magnitude, respectively (U=3/3-/3-/3).

[10][11][23][24][a] According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Mentor measures 117.91 and 126.29 kilometers in diameter and its surface has an albedo of 0.075 and 0.044, respectively.

This minor planet was named by the discoverer from Greek mythology after Mentor, father of Imbrius and son of spearman Imbrus at Pedaseus.