Appellants' application for rehearing, filed July 19, not having been denied by an order of the commission within 20 days, i.e., on or before August 8, became denied "by operation of law" on August 9. The supplemental order issued August 15, 27 days after the application was filed, could not have denied the application which was denied "by operation of law" on August 9, the 21st day after the application was filed. The notice of appeal to this court not having been filed until October 13, 65 days "after the date of denial of the application for rehearing by operation of law," there was a failure on the part of appellants to perfect their appeal within the time required by Section 4903.11, Revised Code. The filing of notice of appeal within the time prescribed by law is a jurisdictional prerequisite in perfecting an appeal. Finfrock v. Public Utilities Commission, 154 Ohio St. 21; In re Complaint of Weber, 154 Ohio St. 209. The motion to dismiss the appeal is sustained.