6 Apps Kids Are Using That Parents Need to Know About 24 May 2018 Published in Hosting & Internet Calculator% Looks like a calculator, but don't be fooled, this and other "calculators" like it are apps used to hide pictures. To access the secret photos in this app you need to type "." (period) then the 4 digit code setup by the user and another "." (period". There is also a paid version of this app with additional features. Read more...