CREATE TABLE table_name_98 (right_ascension___j2000__ VARCHAR(255), constellation VARCHAR(255), ngc_number VARCHAR(255))
Which Right ascension (J2000) has a Constellation of mensa, and an NGC number larger than 2171?
    
SQL: SELECT right_ascension___j2000__ FROM table_name_98 WHERE constellation = "mensa" AND ngc_number > 2171