The Pro Version of Android's tiniest Notepad app with password. You can find the free version here.

https://play.google.com/store/apps/details?id=com.panagola.app.safenotes

Apart from being a versatile Auto Save Notepad with industry-standard password protection for your private notes, it offers the following features over and above the free version.

1) Unlimited notepad slots

2) Inline Checklist capability

3) Search within and across notes

4) Categorize/Bookmark notes

5) Import / Export notes selectively

6) Send text from any external app

7) Make notes read-only to avoid accidental edits

8) Custom themes and colors

9) Full screen view of note and list

10) Lots of configuration options

In spite of the extra features, it is just 0.3mb in size!