The charter of a corporation authorizes the corporation to issue 800,000 shares of common stock and 120,000 shares of preferred stock. Assume that 500,000 common shares were originally issued and 180,000 common shares were re-purchased as treasury stock on 4/30/20. On 5/30/20, half of the treasury stock was sold back onto the market at a price of $45/share. Then, on 7/1/20 a 4% common stock dividend was declared and was paid on 8/1/16. Finally 3,000 shares of treasury stock were purchased on 10/1/2020. No other transactions occurred during 2020. What is the number of common shares outstanding as of 12/31/2020