Britney's biggest digital sales weeks
411,000 "Hold It Against Me" (01/29/11)
303,000 "Womanizer" (01/10/09)
293,000 "S&M [Remix]" (04/30/11)
286,000 "Womanizer" (10/25/08)
286,000 "Circus" (01/10/09)
284,000 "Scream & Shout" (?)
255,000 "3" (10/24/09)
246,000 "Till the World Ends" (05/14/11)
212,000 "Circus" (12/20/08)
203,000 "Scream & Shout" (?)
201,000 "Womanizer" (11/01/08)
196,000 "Scream & Shout" (?)
188,000 "Scream & Shout" (?)
184,000 "Scream & Shout" (?)
183,000 "Hold It Against Me" (02/05/11)
181,000 "Womanizer" (11/08/08)
179,000 "Gimme More" (10/13/07)
178,000 "Circus" (01/17/09)
174,000 "Work Bitch" (09/22/13)
173,000 "Womanizer" (01/17/09)
172,000 "3" (10/31/09)
170,000 "Scream & Shout" (?)
170,000 "Scream & Shout" (?)
162,000 "Scream & Shout" (?)
159,000 "S&M [Remix]" (05/07/11)
158,000 "Gimme More" (10/20/07)
158,000 "Till the World Ends" (03/26/11)
157,000 "Scream & Shout" (?)
153,000 "Circus" (12/27/08)
143,000 "Scream & Shout" (?)
141,000 "Scream & Shout" (?)
139,000 "Scream & Shout" (?)
133,000 "Till the World Ends" (04/23/11)
131,000 "Circus" (01/03/09)
128,000 "Circus" (01/24/09)
126,000 "Till the World Ends" (05/21/11)
125,000 "3" (11/07/09)
122,000 "Scream & Shout" (?)
121,000 "Womanizer" (11/29/08)
120,000 "Scream & Shout" (?)
120,000 "Till the World Ends" (04/30/11)
118,000 "3" (11/21/09)
117,000 "3" (11/28/09)
117,000 "Till the World Ends" (03/19/11)
116,000 "I Wanna Go" (08/06/11)
116,000 "3" (11/14/09)
116,000 "I Wanna Go" (08/13/11)
114,000 "Gimme More" (10/27/07)
113,000 "Hold It Against Me" (02/12/11)
111,000 "Till the World Ends" (06/04/11)
111,000 "Circus" (01/31/09)
109,000 "I Wanna Go" (08/20/11)
107,000 "Circus" (02/07/09)
104,000 "Scream & Shout" (?)
103,000 "I Wanna Go" (08/27/11)
100,000 "Womanizer" (12/13/08)
Total: 56
All of this 10+ years into her career too
(Well except Gimme More which was 9 years but it's basically the same thing lbr)