
The first three singles from
21 ("Rolling in the Deep", "Someone Like You", and "Set Fire to the Rain") were all #1 singles. "Rumour Has It", the fourth and final international single (the international release of the fifth single, "Turning Tables", was scrapped and it was only released unofficially in the US and officially in select European countries), flopped on the charts, peaking at #16, but that was due to her vocal surgery and her taking a break from music, and it still did really well commercially, so... Technically, the era wasn't a flop. The album became one of the best-selling albums of all-time as it was, and was certified Diamond. I'm pretty sure that the 21 era was not a flop at all.