…and I use the word “riddle” loosely.
How many apostrophes are in this quote?
So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
O death, where is thy sting? O grave, where is thy victory?
Hint: it’s not zero.
If anybody gets this, they probably need to go outside more.
Brian D. Buckley 
As the speaker is alive and above ground, I’m going to say two.
Nailed it!
One for you, then: would the question have been easier if asked aloud?
About the same, I would think. Maybe slightly more difficult, since there’d be no way to visually verify the lack of punctuation apostrophes.
Correct. The words are homonyms as well as homographs.
2 ?
You got it.