|No. in Series|No. in Season|Performer|Appearance|Air Date|
|---|---|---|---|---|
|268|1|Tom Segura|only|21 January 2011|
|269|2|Michael Kosta|only|21 January 2011|
|270|3|Sheng Wang|only|28 January 2011|
|271|4|Chelsea Peretti|only|28 January 2011|
|272|5|Chris D'Elia|only|4 February 2011|
|273|6|Nate Bargatze|only|4 February 2011|
|274|7|Hari Kondabolu|only|11 February 2011|
|275|8|Jack Whitehall|only|11 February 2011|
|276|9|Al Jackson|only|18 February 2011|
|277|10|Kyle Kinane|only|25 February 2011|
|278|11|Matt Fulchiron|only|25 February 2011|
|279|12|Mike Vecchione|only|4 March 2011|
|280|13|Jessi Klein|only|4 March 2011|
|281|14|Louis Katz|only|11 March 2011|
|282|15|Jay Larson|only|11 March 2011|
|283|16|Natasha Leggero|only|25 March 2011|

Question: how many performers appeared on the air date 21 january 2011?
Answer: 2