The figure was shared exclusively with Mashable by Photogram maker Timelines. The application's early success is comparable to red hot social camera application Instagram, which also attracted 100,000 users in its first week.
"It fulfills a need that was previously unsatisfied," explains Timelines CEO Bob Armour. "You can tell a story using multiple photos that are wrapped in a beautiful and memorable context and deliver it easily to people that are important to you."
Photogram [iTunes link] has been downloaded in 152 countries, and 75% of its users are sending Photograms with three or four photos, the startup reports.
The app also appears to be especially popular with women -- the startup estimates that 70% of users are female -- and that's by design.
"We targeted the app for young parents, and specifically young moms, because we felt that their needs weren’t being met," Armour says. "It seems that these needs are more universal than we expected."