21642

21642 is a numbered minor planet in the asteroid belt, located between the orbits of Mars and Jupiter. It is officially designated as (21642) and belongs to the main-belt population. The asteroid was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) survey at the Socorro site in New Mexico on 19 March 1998. Its provisional designation was 1998 CR12.

The orbit of 21642 has a semi-major axis of about 2.45 astronomical units, an eccentricity of 0.12, and an inclination of roughly 5.4 degrees to the ecliptic. It completes one revolution around the Sun every 3.8 Earth years. The mean anomaly, argument of perihelion, and longitude of ascending node are typical for central main-belt asteroids. The observation arc spans more than twenty years, providing a well-determined orbit with a uncertainty parameter of 0.

Physical characteristics inferred from photometric observations suggest that 21642 is a stony (S-type) asteroid with an estimated diameter of approximately 5 kilometers, assuming an albedo around 0.20. Its rotation period, as derived from lightcurve analysis, is about 4.2 hours, with a moderate brightness variation indicative of a slightly elongated shape. Spectral data from the Sloan Digital Sky Survey (SDSS) support the S-type classification, though detailed spectroscopy is lacking.

210 show no current plan for naming, and as of the latest database updates, the minor planet remains unnamed. It has not been observed to exhibit any cometary activity or other unusual behavior. Its taxonomic classification, orbital parameters, and size place it among the many kilometer-sized bodies that populate the main asteroid belt.