Billed as the last Beatles song, "Now And Then" features the voice of late member John Lennon and was developed using artificial intelligence.
The song also features parts recorded by surviving members Paul McCartney and Ringo Starr as well as the late George Harrison.
The group is also the act with the longest gap between No. 1 singles - 54 years - and the oldest band to score a UK No. 1 single, the Official Charts Company said. McCartney is 81 while Starr is 83.