In case you have NA's:
sapply(data, mean, na.rm = T) # Returns a vector (with names)
lapply(data, mean, na.rm = T) # Returns a list
Remember that "mean" needs numeric data. If you have mixed class data, then use:
numdata<-data[sapply(data, is.numeric)]
sapply(numdata, mean, na.rm = T) # Returns a vector
lapply(numdata, mean, na.rm = T) # Returns a list