21641

21641 is a minor planet in the asteroid belt, located between the orbits of Mars and Jupiter. It was discovered on 24 September 1960, by the Indiana Asteroid Program at Goethe Link Observatory. The asteroid is named after the year of its discovery, 1960, which is represented in Roman numerals as MMCLX.

21641 has an estimated diameter of approximately 10 kilometers. Its orbit has a semi-major axis of about 2.7 astronomical units (AU), with an orbital period of roughly 4.5 Earth years. The asteroid's orbital eccentricity is 0.11, and its inclination to the ecliptic is about 11 degrees.

The spectral type of 21641 is not well-determined, but it is likely to be an S-type asteroid, which are composed mainly of silicate materials. This classification is based on its reflectance spectrum, which is similar to that of stony meteorites.

The asteroid's rotation period is not precisely known, but it is estimated to be around 5.5 hours. This is based on photometric observations that show variations in the asteroid's brightness, which are likely due to its rotation.

21641 is not a potentially hazardous asteroid, as its orbit does not bring it close to Earth's orbit. However, its discovery and ongoing study contribute to our understanding of the asteroid belt and the formation of the solar system.