Sell my AAPL to pay down Mortgage?

[Doug Spence]

Hi Everyone! I purchased 32 shares of AAPL a few years ago, and it has nearly tripled in value since. I own two investment properties (closing on my third in two days), and I want to start paying down these mortgages, in addition to saving for more properties. 

Here are the numbers:

32 Shares AAPL current mkt value - $6,384 

Long-term capital gains tax (20%) - $820

Total amount left to invest in mortgage - $5,564

Principal left on mortgage - $62,000

Interest rate - 5.25%

I want to pay down this particular mortgage first because it has the smallest principal remaining, and the highest interest rate. I save enough from my W-2 job to meet my goal of purchasing one property per year, while also putting about 25% of my income into retirement accounts, so I would use this money to pay down the mortgage.

Do I capture AAPL around $200/share right now to pay towards the mortgage? Standing by for thoughts and suggestions...