"Since most individual holders hold through street name and not in registered name, this is not a good proxy for actual number of holders. For instance, this is what Facebook says in their most recent 10-K filing in response to this item.

"As of December 31, 2013, there were 4,819 stockholders of record of our Class A common stock, and the closing price of our Class A common stock was $54.65 per share as reported on the NASDAQ Global Select Market. Because many of our shares of Class A common stock are held by brokers and other institutions on behalf of stockholders, we are unable to estimate the total number of stockholders represented by these record holders. As of December 31, 2013, there were 102 stockholders of record of our Class B common stock"

https://www.quora.com/Is-there-a-way-to-know-...s-in-total