Even at $99, Amazon (NASDAQ:AMZN) Prime offers tremendous value.

Unfortunately, Amazon doesn't disclose the exact number of Prime subscribers that it has, but estimates commonly peg the figure at around 40 million to 60 million. With so many benefits, it's easy to see why. Most are well aware of the free two-day shipping Prime members enjoy, but there are several less heralded perks that can be just as enticing. Below are five Prime perks everyone should be aware of.

1. Unlimited cloud storage for photos
Amazon Prime members can back up an unlimited number of their photos to the cloud. By installing the Amazon Photo app on their smartphone or tablet, they can sync their photos to Amazon's cloud automatically, over Wi-Fi or with their smartphone's data plan. Video storage is not unlimited, but Amazon Prime subscribers can also store 5GB worth of video for free.

This represents a significant value, particularly for heavy photographers that use an iPhone. Apple includes 5GB of iCloud storage with every iTunes account, but that can be filled up rather quickly. Apple charges for additional storage on a monthly basis, with 200GB costing nearly $50 per year. That's almost half the cost of Amazon Prime, but without all the other perks.

2. Listen to millions of songs for free
An Amazon Prime membership also includes access to Amazon Prime Music, its free streaming music service. Although Prime Music doesn't offer as robust a catalog as some of the other streaming music services (such as Spotify or Rdio), it offers millions of songs on demand. Since its debut last year, Amazon has continued to update and improve the service: in March it added ad-free radio stations. 

3. Borrow Kindle books
The unlimited photo storage and music on demand are both accessible from virtually any smartphone or tablet -- Amazon makes its apps available for both iOS and Android devices. The Kindle lending library, however, is not. To take advantage of it, Prime subscribers will also need to own an Amazon Kindle device.

But if they have one, Amazon Prime subscribers can "borrow" an unlimited number of eBooks for free. Only one can be "lent" at a time, and not every eBook Amazon sells is included in the program, but for voracious readers, it's another reason to subscribe to Amazon's service. 

4. Watch thousands of hit shows
Prime's best known perk beyond free two-day shipping may be its streaming Internet video. It's cheaper than Netflix ($99 vs. $108 annually), and it's increasingly just as enticing.

Amazon has locked up the exclusive streaming rights to the variety of hit shows, including a great deal of Viacom's Comedy Central, Nickelodeon, and MTV content, as well as HBO's older original programming. Amazon also has a growing number of original programmings, including the Golden Globe-winner Transparent.

Prime Pantry box. Photo: Amazon.com

5. Get groceries delivered
Amazon Prime subscribers can take advantage of Amazon Prime Pantry, an exclusive service that lets you purchase a variety of household goods.

For a flat rate of $6, Amazon Prime subscribers can ship a box of "pantry" items -- generally long-lasting food and cleaning supplies (soda, soup, cereal, shampoo, soap, and pet food, among hundreds of other items) to their home. As you shop pantry items, Amazon will let you know what percentage of a pantry box a given item takes up, and how many pantry boxes your current order requires.

Frankly, the prices are not as great as the many large supermarkets or bulk stores you can find in suburban shopping centers, but for urban-dwellers, it can be easier and significantly cheaper than shopping at the local corner store.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.