Please answer a question about the following article about Santa Monica, California:

As of the census of 2000, there are 84,084 people, 44,497 households, and 16,775 families in the city. The population density is 10,178.7 inhabitants per square mile (3,930.4/km²). There are 47,863 housing units at an average density of 5,794.0 per square mile (2,237.3/km²). The racial makeup of the city is 78.29% White, 7.25% Asian, 3.78% African American, 0.47% Native American, 0.10% Pacific Islander, 5.97% from other races, and 4.13% from two or more races. 13.44% of the population are Hispanic or Latino of any race. There are 44,497 households, out of which 15.8% have children under the age of 18, 27.5% are married couples living together, 7.5% have a female householder with no husband present, and 62.3% are non-families. 51.2% of all households are made up of individuals and 10.6% have someone living alone who is 65 years of age or older. The average household size is 1.83 and the average family size is 2.80.

What is the population density per square mile?
10,178.7