<PAGE>
October 2, 1998
Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 25049-1004
Attention: Filing Desk
Mail Stop 1-4
1933 Act File No. 333-63847
1940 Act File No. 811-08103
Re: Nuveen Unit Trusts, Series 21 (the "Trust")
-------------------------------------------
Ladies/Gentlemen:
On behalf of John Nuveen & Co. Incorporated and in accordance with the
provisions of Rule 497(j) of Regulation C under the Securities Act of 1933 (the
"Securities Act"), this letter serves to certify that the form of prospectus and
Information Supplement contained in the most recent amendment to the
Registration Statement on Form S-6 (the "Registration Statement") of the above
referenced Series does not differ from that which would have been filed pursuant
to Rule 497(b) of the Securities Act. Amendment No. 1, which was the most recent
amendment to the Registration Statement, was filed electronically with the
Commission on September 30, 1998.
Very truly yours,
CHAPMAN AND CUTLER
By /s/ MORRISON C. WARREN
----------------------------
Morrison C. Warren
Enclosure
cc: Alan G. Berkshire
