The Sprint Spark variant of the Galaxy S4 is a special version of that device. Arriving 8 months after the original version, this limits Lollipop’s rollout only to people who bought the Galaxy S4 after a specific amount of time.
However, with the Spark variant getting Lollipop, there’s a very high chance of the original Galaxy S4 getting Lollipop as well. For the Spark, the build number is L720TVPUCOD1. Sprint doesn’t say how big the update is, but it’s probably large, so make sure to be on Wifi.
You can check in the settings menu for your OTA update but if it doesn’t show up you may have to wait a few days for it to appear. Those of you with this device, are you glad you’re not being left out of Lollipop?