Fastest selling single?

On February 1st 1964, the Beatles officially reached number one on the U.S. Billboard Top 100. Six days later, they landed in New York for the first time.
During that first brief visit, previously released singles chased I WANT TO HOLD YOUR HAND up the chart. By mid-March, they held the top four places.
Written by Paul on a grand piano in his hotel suite, it was, in his words, 'very hooky'
Now they needed a new single to cash in on the hot streak. They recorded the song between gigs in Paris and days before leaving London.
Written by Paul on a grand piano in his hotel suite, it was, in his words, 'very hooky'
Sales
With an unprecedented advance sales of 2.7 million, the US release was pushed forward to March 16, four days before it came out in Britain. 900,000 physical copies sold on the first day alone.
It spent five weeks at No. 1 on the Billboard Hot 100 and stayed on the chart for 10 more weeks.
In the summer, CAN'T BUY ME LOVE received a further promotional boost with the worldwide release of the feature film A Hard Day's Night, where it featured in the celebrated 'dancing in the field' scene.
CAN'T BUY ME LOVE holds the Guinness World Record for the fastest-selling commercial single.
The story behind CAN'T BUY ME LOVE (4 min Medium free read)