Error: 21659, Severity: 16, Cannot execute this procedure for a SQL Server Publisher. The Publisher must be a non-SQL Server Publisher.
Error: 21660, Severity: 16, The value specified for the parameter @full_or_fast for article ‘%s’ must be 0, 1, or 2.
Error: 21661, Severity: 16, The value specified for the @shutdown_agent parameter for article ‘%s’ must be 0 or 1.
Error: 21662, Severity: 16, The source object [%s].[%s] on the non-SQL Server Publisher was either not found or is not supported. If the object exists, verify that it meets the requirements for being published.

Error: 21663, Severity: 16, Cannot find a valid primary key for the source table [%s].[%s]. A valid primary key is required to publish the table. Add or correct the primary key definition on the source table.
Error: 21664, Severity: 16, Index [%s] contains unique nullable column.
Error: 21665, Severity: 16, Key [%s] contains unique nullable column.
Error: 21666, Severity: 16, Cannot specify more than %d column names for the index or primary key because this exceeds the maximum number of columns supported by SQL Server. %d columns were specified.

Error: 21667, Severity: 16, The index “%s” was not created. The index has a key length of at least %d bytes. The maximum key length supported by SQL Server is %d bytes.
Error: 21668, Severity: 16, The constraint “%s” was not created because one or more columns in the constraint is not published. Either include all columns in the published article, or alter the constraint to remove columns that are not published.
Error: 21669, Severity: 16, Column [%s] cannot be published because it uses an unsupported data type [%s]. View supported data types by querying msdb.dbo.sysdatatypemappings.
Error: 21670, Severity: 16, Connection to server [%s] failed.
Error: 21671, Severity: 16, Cannot execute the procedure. Administration of a non-SQL Server Publisher must be performed at the associated SQL Server Distributor. Execute the procedure at the Distributor.
Error: 21672, Severity: 16, The login ‘%s’ has insufficient authorization to execute this command.
Error: 21673, Severity: 16, Test connection to publisher [%s] failed. Verify authentication information.
Error: 21674, Severity: 16, Unable to update the linked server [%s] for the login [%s].
Error: 21675, Severity: 16, Cannot specify more than %d indexes for a single table. %d indexes specified. Excess indexes have been ignored.
Error: 21676, Severity: 16, Heterogeneous subscriber ‘%s’ could not add a subscription for heterogeneous publication ‘%s’ because publication sync method is not ‘character’, ‘concurrent_c’, or ‘database snapshot character’.
Error: 21677, Severity: 16, Heterogeneous publisher ‘%s’ cannot be defined as a subscriber.
Error: 21678, Severity: 16, The parameter “%s” can be set to “%s” only when “%s” is set to “%s”.

This is applicable on below versions of SQL Server

SQL Server 2005
SQL Server 2008 R2
SQL Server 2012
SQL Server 2014

Hope this was helpful.

Thanks,
SQLServerF1 Team
In-Depth Blogs on SQL Server, Information about SQL Server Conferences and Events, SQL Server Frequently asked questions, SQL Server Trainings.