[2][10] Hirayama orbits the Sun in the outer main-belt at a distance of 2.8–3.5 AU once every 5 years and 6 months (2,010 days).

[1] The spectrum of Hirayama matches a C-type classification on the Tholen taxonomic scheme, but with a "broad absorption band that can be associated to a process of aqueous alteration".

[7] At the same time, photometric observations by astronomers Roberto Crippa and Federico Manzini gave a rotation period of 22.37 hours and a brightness variation of 0.47 magnitude (U=2).

[a] According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures between 34.0 and 38.3 kilometers in diameter and its surface has an albedo between 0.053 and 0.088.

[4][5][6] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.062 and a diameter of 33.8 kilometers with an absolute magnitude of 11.0.