Share what SAS code you are using, preferably in a SAS-generated log with all code revealed. Also, your SAS version, OS platform, whether running SAS local or remote (connection) is always helpful with getting an accurate and effective reply from forum subscribers.
So, if your point: "I would like to keep #ID when I output the post-processed data file" means that you want to have the first observation contain the data-string found in the header record of your input data, consider that the remaining observations (for the #ID variable) must also be CHARACTER, instead of NUMERIC. This will present challenges with sorting data.
You may want to clarify what your INPUT data looks like and also what you would like to see any OUTPUT (report, SAS dataset) look like. And also clarify why you want the #ID, given that the remaining rows are "numerical numbers".
Scott Barry
SBBWorks, Inc.