Kolkata, also known as Calcutta, is the capital and largest city of the Indian state of West Bengal. It lies on the eastern bank of the Hooghly River, 80 km (50 mi) west of the border with Bangladesh. It is the primary financial and commercial centre of eastern and northeastern India. Kolkata is the seventh most populous city of India with an estimated city proper population of 4.5 million (0.45 crore). It is the centre of the Kolkata Metropolitan Region, one of the most populous metropolitan areas in the world with a population of over 15 million residents. Kolkata is the regarded by many sources as the cultural capital of India and a historically and culturally significant city in the historic region of Bengal. It is the second largest Bengali-speaking city in the world. It has the highest number of Nobel laureates among all cities in India.