21520+3857
- Unique Name: 21520+3857COU1823
- RA: 21 52 02.50
- Dec: +38 57 16.5
- Discoverer: COU
- Discoverer Number: 1823
- Components:
- First year: 1979
- Last year: 2010
- Observations: 5
- First position angle: 6
- Last position angle: 12
- First separation: 1.2
- Last separation: 1.0
- Mag first component: 7.69
- Mag second component: 11.54
- Spectral type: K0
- Primary proper motion RA: 93
- Primary proper motion DEC: 23
- Secondary proper motion RA: 93
- Secondary proper motion DEC: 26
- Durchmusterung: +38 4625
- Notes: