If you mean Citizens Bank of Massachusetts, they merged with RBS Citizens, two years ago...
Citizens Bank Of Massachusetts
Headquartered In: Boston, Massachusetts (L-I-R™ No. 760280)
Now RBS CITIZENS, N.A.
Headquartered In: Providence, Rhode Island (L-I-R™ No. 331886)
Date Recorded: 09/2007
Reason: Commercial Merger
(this info was found at http://www.laneguide.com)
If this is what you are looking for, you can find the routing number for RBS at http://www.findroutingnumbers.com, just enter the bank's name.
011500120
citizen
211170114
036076150
011401533
RBS Citizens Bank
The routing number is 211070175.
011500120
211170114
citizen
011401533
036076150
Citizens Bank in Massachusetts.
011401533
211070175
021313103
Statewide Citizens Bank PA routing number = 036076150 ALL of PA and only PA per their customer service 05/09/09