Since it got over, there have been many speculations(statistical, logical....) in the official groups about the no. of entries received. Google has put an end to it on their blog in which Azhar Hashem, Product Marketing Manager for Android said, "I'm thrilled to share the news that developers from over 70 countries submitted 1,788 entries to the Android Developer Challenge!". So there you have it, the official number is 1788.
Hashem also mentioned that the rate of submission had jumped to 170+ submissions per hour in the early hours of Tuesday. Sharing some more statistics, about 600 entries were from US and rest from Germany, Japan, China, India, Canada, France, UK, and other countries.
The judging process will begin soon in which over 100 judges,experts from within OHA and the mobile industry, will rate each of the apps on the basis of 4 criteria, assigning score of 1 -to 10 for each of the criteria. The results, 50 Semi-finalists who will be awarded $25,000 each, will be declared around May 5.
Best of luck to all the participants !