How many princely states joined India?

Through the efforts of Sardar Vallabhai Patel, about 562 princely states joined India. Before the Partition of India in 1947, about 584 princely states, also called “native states”, existed in India, which were not fully and formally part of British India,

Upon Independence, they were given the choice of either joining India or Pakistan or remaining independent. Through tact and diplomacy Sardar Vallabhai Patel managed to integrate many princely states within the Union of India.

For further reading check the following articles:

• Portuguese India
• British Raj
• Dutch Colonialism in India