That compares to an estimated 1.8 million Muslims who take part in the annual hajj pilgrimage to Mecca in Saudi Arabia.
Indian police said they were “conducting relentless day-and-night patrols to ensure top-notch security” for the event.
Authorities and the police have also set up a network of “lost and found” centres and an accompanying phone app to help pilgrims lost in the immense crowd “to reunite with their families”.
India is the world’s most populous nation, with 1.4 billion people, and so is used to large crowds.
Many pilgrims began taking dips in the chilly water on Sunday, braving rain, with temperatures on the banks dropping to around 15 degrees Celsius (59 Fahrenheit) overnight.
But many pilgrims threw off their plastic sheets, insisting rain only added to the “pious mood” of the fair.
