Question: What was the population of the city where Nalanda Open University is located in 2011?

Context paragraphs:
Dr. B.R. Ambedkar Open University: Dr. B.R. Ambedkar Open University, also known as Telangana Open University, formerly Andhra Pradesh Open University, is a public university in the city of Hyderabad, Telangana, India.

Patna: Patna , is the capital and largest city of the state of Bihar in India.  It had an estimated population of 1.68 million in 2011, making it the 19th largest city in India.  With over 2 million people, its urban agglomeration is the 18th largest in India.  Patna also serves as the seat of Patna High Court.

Uttarakhand Open University: Uttarakhand Open University (Hindi: उत्तराखण्ड मुक्त विश्वविद्यालय ) is an Open University located in the city of Haldwani in the Indian state of Uttarakhand.

Ho Chi Minh City Open University: Ho Chi Minh City Open University (Vietnamese: "Đại học Mở Thành phố Hồ Chí Minh" ) is a public university located in District 3, Ho Chi Minh City, Vietnam.  This is the first open university in Vietnam.  The university was initially Ho Chi Minh City Open and Semi-Private University established in June 15, 1990, then it obtained the present name on June 26, 2006.

Biscomaun Bhawan: Biscomaun Bhawan is the tallest building in Patna and Bihar.  It is a public building that houses many of the administrative offices of Bihar.  It is 71 meters high.  It houses many important offices of the Bihar government, the Government of India, some private company offices, and the Nalanda Open University.  It is the only building with a revolving restaurant (Pind Balluchi), and a software park in all of Bihar and Eastern India.

Indira Gandhi National Open University: The Indira Gandhi National Open University (Hindi: इंदिरा गाँधी राष्ट्रीय मुक्त विश्वविद्यालय ), known as IGNOU, is a distance learning national university located in Maidan Garhi, New Delhi, India.  Named after former Prime Minister of India Indira Gandhi, the university was established in 1985 with a budget of 20 million, after the Parliament of India passed the "Indira Gandhi National Open University Act, 1985" (IGNOU Act 1985).  IGNOU is run by the central government of India, and with over 4 million students, claims to be the largest university in the world.

Venkateshwara Open University: Venkateshwara Open University (VOU) is a state private University located in Naharlagun, Arunachal Pradesh, India.  It was established by the Venkateshwara Open University Act No.10 of 2012 of the Government of Arunachal Pradesh in 2012.  VOU is empowered to award degrees by the University Grants Commission (UGC).  VOU is a member of the Association of Indian Universities (AIU).

Ravindra Kumar Sinha (biologist): Dr. Ravindra Kumar Sinha (born 1 July 1954) is an Indian biologist and environmentalist.  Currently, he is Vice Chancellor for Nalanda Open University; previously he was the Head of the Department of Zoology at Patna University, and is a pioneer researcher and wildlife conservationist, popularly known as the "Dolphin Man of India", famous for his efforts for the conservation of Gangetic Dolphins.  His scientific research and relentless conservation campaign for the past 35 years have been crucial to the efforts of saving the Ganga River dolphin from extinction.  In response to the awareness of the urgency of protecting the Ganga River dolphin raised by Dr. Sinha, the Government of India designated this Dolphin as the National Aquatic Animal of India in 2009.

Open University of Israel: The Open University of Israel (Hebrew: האוניברסיטה הפתוחה‎ , "Ha-Universita ha-Ptuha") is a distance-education university in Israel.  Its administration center is located in the city of Ra'anana.  s of 2006 , the Open University had taught around 39,000 students.

Nalanda Open University: Nalanda Open University (NOU) is a university at Patna in Bihar state, India.

Supporting paragraphs: Nalanda Open University Patna
Answer: 1.68 million