Low memory on iPad 2

Memory is RAM - random access memory.

The 21.5 GB is your available storage capacity - apples and oranges.

You're welcome.

What problem are you having?

Then there is not a problem.

Have you heard of the saying - "if it isn't broke, don't fix it."?

Don't go looking for problems that don't exist.

I had this same issue with the new ipad, I kept getting logs generated that stated low memory. I am not aware of any problems or issues this created, it was just sort of an informational warning not that there was anything wrong. To “fix” it I just closed all the apps still in memory by double clicking the home button, holding your finger on one of the apps in the bottom window until they shake then hit the x to close them out of memory.