BTS has claimed their seventh No. 1 album on the Billboard 200 with ARIRANG, their first full group project in nearly four years since completing mandatory military service. The album opened with 641,000 equivalent album units earned in its first tracking week, the largest opening week for an album by a group since Billboard began measuring by equivalent album units in December 2014. The debut cements what many had already suspected since the album’s release on March 20: that the group’s return from a years-long hiatus, one defined by solo careers and mandatory service, had done nothing to diminish their grip on the global music market. The numbers behind the debut are staggering across every metric. Of ARIRANG’s 641,000 equivalent album units, pure album sales comprise 532,000, the group’s biggest sales week ever, while streaming equivalent album units comprise 95,000, equaling 99.10 million on-demand official streams, also BTS’ biggest streaming week ever for an album. Physical sales drove much of the chart performance, according to a report by Billboard. ARIRANG’s first-week sales were largely powered …