Delhi , officially the National Capital Territory of Delhi, is a city and the capital territory of the Republic of India.It is bordered by Haryana on three sides and by Uttar Pradesh to the east. It is the most expensive city in India—about 1,484 square kilometres . It has a population of about 25 million, making it the second most populous city after Mumbai and most populous urban agglomeration in India and 3rd largest urban area in the world. Such is the nature of urban expansion in Delhi that its growth has expanded beyond the NCT to incorporate towns in neighbouring states and at its largest extent can count a population of about 25 million residents as of 2014. After Mumbai, Delhi has the second-highest number of billionaires and millionaires among all cities in India.