Fun.'s "We Are Young," featuring Janelle Monae, tops the Billboard Hot 100 songs chart for a fifth week, just holding off Justin Bieber's "Boyfriend," which bounds in at No. 2 with the second-highest-ever debut digital sales week.

"Boyfriend" opens atop the Hot Digital Songs chart with 521,000 first-week downloads sold, according to Nielsen SoundScan. Since SoundScan began tracking digital sales (which first contributed to the Hot 100 the week of Feb. 12, 2005), only Flo Rida's "Right Round" has debuted on Hot Digital Songs with a higher total (636,000, the week of Feb. 28, 2009).

Justin Bieber's 'Boyfriend' Breaks First-Week Airplay Record on Billboard Mainstream Top 40 Chart

The opening digital sales total for "Boyfriend" is also the fourth-best for any song, debut or already charted. Here are the all-time top five digital sales weeks, according to SoundScan:

636,000, "Right Round," Flo Rida, Feb. 28, 2009
610,000, "TiK ToK," Ke$ha, Jan. 9, 2010
559,000, "Grenade," Bruno Mars, Jan. 8, 2011
521,000, "Boyfriend," Justin Bieber, April 14, 2012
509,000, "Born This Way," Lady Gaga, March 5, 2011

"Boyfriend" likewise logs an impressive first week of airplay, debuting at No. 24 on the Hot 100 Airplay chart with 40 million audience impressions, according to Nielsen BDS. Among newly-released songs by male soloists in the chart's 21-year history, only two have arrived with greater audience totals: Eminem's "Just Lose It" (52 million, Oct, 9, 2004) and Michael Jackson's "Black or White" (41 million, Nov. 23, 1991).

As previously reported, "Boyfriend" registered a history-making bow on the Mainstream Top 40 radio airplay chart, launching with 3,961 first-week plays, the best first-week plays sum for a song by a male artist in the list's almost 20-year archives.

With its No. 2 start, Bieber notches his highest Hot 100 placement. He had previously ranked as high as No. 5 when "Baby" debuted (and peaked) at No. 5 the week of Feb. 6, 2010. (He boasts one other Hot 100 top 10: "Never Say Never" (No. 8, 2011), featuring Jaden Smith.)

Despite the massive first-week numbers for "Boyfriend," fun.'s "We Are Young" leads the Hot 100 for a fifth week. The song slips 1-2 on Hot Digital Songs with 363,000 downloads sold (down 6%). On Hot 100 Airplay, "Young" pushes 4-2 with 104 million audience impressions (up 19%), enough to give the song top Airplay Gainer honors on the Hot 100 for a fifth consecutive week. The song is the first by a group to link five straight such awards since the Black Eyed Peas' "I Gotta Feeling" also earned the honor over five straight weeks in summer 2009.

A notable factor in the chart battle between "Boyfriend" and "Young" is the latter song's upper hand in streaming. "Young" remains atop the On-Demand Songs chart with 1.18 million on-demand streams (flat from last week) in the chart's tracking week, according to BDS.

"Boyfriend," however, logs almost no streaming points among its Hot 100 points total due to its lack of availability on most streaming services during the tracking week, which ended Sunday (April 1). Also granting an edge to "Young," albeit slight, was the song's availability at all digital retailers, while "Boyfriend" was released as an iTunes-exclusive track.

Below the tightly-contested fight to the finish atop the Hot 100 this week, other action abounds.

Gotye's "Somebody That I Used to Know," featuring Kimbra, rises 4-3. The collaboration, which tops Alternative for a seventh week, dips 2-3 on Hot Digital Songs but with a 17% gain to 244,000 downloads sold. It advances 20-16 on Hot 100 Airplay (52 million, up 23%) and remains at No. 2 on On-Demand Songs (961,000, up 10%).

U.K. boy band the Wanted slips 3-4 on the Hot 100 with "Glad You Came." The song falls 3-8 on Hot Digital Songs (169,000, down 8%) but continues its ascent on Hot 100 Airplay, where it climbs 6-4 (95 million, up 15%). On On-Demand Songs, "Glad" descends 3-4 but with a 3% uptick to 645,000.

Kelly Clarkson's former three-week No. 1 "Stronger" rounds out the Hot 100's top five, dropping 2-5. Nicki Minaj's "Starships" slides 5-6 and Flo Rida's "Wild Ones," featuring Sia, and Katy Perry's former leader "Part of Me" hold at Nos. 7 and 8, respectively.

Two pure pop acts, meanwhile, score Hot 100 top 10s in their first chart appearances.

One Direction, the top tier's other British boy band phenomenon in addition to the Wanted, jumps 11-9 with "What Makes You Beautiful." The song rises 7-5 on Hot Digital Songs (199,000, up 22%), 53-42 on Hot 100 Airplay (32 million, up 21%) and 15-11 on On-Demand Songs (476,000, up 22%).

At No. 10, Carly Rae Jepsen's "Call Me Maybe" darts from No. 18 as the Hot 100's top Digital Gainer. The track roars 9-7 on Hot Digital Songs (182,000, up 32%), debuts on Hot 100 Airplay at No. 73 (15 million, up 80%) and jumps 5-3 on On-Demand Songs (662,000, up 24%). The song's success is yet another sign of Bieber's influence, as, as previously reported, he has championed "Maybe" through various forms of social media.

"Maybe" recently spent four weeks at No. 1 on the Billboard Canadian Hot 100. This week, "Boyfriend" opens atop Bieber's home country's signature chart, marking his first Canadian Hot 100 No. 1.

Check tomorrow (April 5), when all rankings, including the Hot 100, Hot Digital Songs, Hot 100 Airplay and On-Demand Songs, will be refreshed, as they are each Thursday.