Investigators say the teen rode up to the 13-year-old on a Citi Bike and demanded his wallet and cell phone.
It happened Monday on Central Park West at 1:45 p.m.
The robber ran off with the teenager's phone and $100 in cash from his wallet.
The victim was not injured.
The 17-year-old is not being identified due to his age.
Anyone with information in regard to this incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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