PROSPECTUS SUPPLEMENT                                         File No. 333-52822
---------------------                                             Rule 424(b)(3)
(To Prospectus Supplement and Prospectus
dated January 24, 2001)
Prospectus number:      2173


                             Merrill Lynch & Co., Inc.
                           Medium Term Notes, Series B
                   Due Nine Months or More from Date of Issue


                               Floating Rate Notes


Principal Amount:  $5,000,000         Original Issue Date:    September 26, 2001

CUSIP Number:      59018Y KR1         Stated Maturity Date:   June 1, 2004


Interest Calculation:                  Day Count Convention:
---------------------                  ---------------------
[X]  Regular Floating Rate Note        [X]  Actual/360

[ ]  Inverse Floating Rate Note        [ ]  30/360

       (Fixed Interest Rate):          [ ]  Actual/Actual


Interest Rate Basis:
--------------------
[X]  LIBOR                             [ ]  Commercial Paper Rate

[ ]  CMT Rate                          [ ]  Eleventh District Cost of Funds Rate

[ ]  Prime Rate                        [ ]  CD Rate

[ ]  Federal Funds Rate                [ ]  Other (see attached)

[ ]  Treasury Rate

   Designated CMT Page:                Designated LIBOR Page:
        CMT Telerate Page:                  LIBOR Telerate Page:
        CMT Reuters Page:                   LIBOR Reuters Page:


Index Maturity:        Three Month         Minimum Interest Rate: Not Applicable

Spread:                0.2200%             Maximum Interest Rate: Not Applicable

Initial Interest:      TBD                 Spread Multiplier:     Not Applicable



Interest Reset Dates:      Quarterly, on the 1st of March, June, Sept. and Dec.,
                           commencing December 1, 2001 until maturity, subject
                           to modified following business day convention.

Interest Payment Dates:    Quarterly, on the 1st of March, June, Sept. and Dec.,
                           commencing December 1, 2001 until maturity, subject
                           to modified following business day convention.

Repayment at the
Option of the Holder:      The Notes cannot be repaid prior to the Stated
                           Maturity Date.

Redemption at the
Option of the Company:     The Notes cannot be redeemed prior to the Stated
                           Maturity Date.

Form:                      The Notes are being issued in fully registered
                           book-entry form.

Trustee:                   The Chase Manhattan Bank

Dated:                     September 20, 2001