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
citizen
211170114
031101143 - not the one on mainstreet but the one up by the PA - line.
011401533
036076150
011401533
211070175
Citizens Bank in Massachusetts.
021313103