Organization	9 Months Ended
Organization	Sep. 30, 2025
Accounting Policies [Abstract]
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	(2) Organization – AEI Income & Growth Fund XXI Limited Partnership (the “Partnership”) was formed to acquire and lease commercial properties to operating tenants. The Partnership’s operations are managed by AEI Fund Management XXI, Inc. (“AFM”), the Managing General Partner. The Estate of Robert P. Johnson serves as the Individual General Partner. AFM is a wholly owned subsidiary of AEI Capital Corporation of which the Credit Trust fbo Patricia Johnson and Patricia Johnson own a majority interest. AEI Fund Management, Inc. (“AEI”), an affiliate of AFM, performs the administrative and operating functions for the Partnership. In January 2021, the Managing General Partner mailed a Consent Statement (Proxy) seeking the consent of the Limited Partners to continue the Partnership for an additional 60 months or to initiate the final disposition, liquidation and distribution of all of the Partnership’s properties and assets. On March 3, 2021, the votes were counted and neither proposal received the required majority vote. As a result, the Managing General Partner will continue the operations of the Partnership for an additional 60 months at which time it will ask the Limited Partners to vote on the same two proposals.

AEI INCOME & GROWTH FUND XXI LTD PARTNERSHIP 10-Q