How can I store a number larger than 2147483647 in PlayerPrefs?

I recently discovered that Unity refuses to save an int larger than 2,147,483,647 in PlayerPrefs. [The reason why this occurs is well-documented][1], but what is a workaround for this problem? I need to store a number that can become incredibly large - indeed, larger than two billion - in PlayerPrefs. How would I go about doing this? [1]: http://en.wikipedia.org/wiki/2147483647