Northern Africa (just answered in apex)
The five highest Muslim population countries are Indonesia (203 millions), Pakistan (174 millions), Bangladesh (145 millions), Egypt (78 millions), and Turkey (74 million. This is as of October 2009 per Pew Forum study shown on the link below.
That bit of Turkey which is in Europe, because Turkey is a Muslim majority state, and also Bosnia would have a high Muslim population (even more so if the Russian Orthodox Serbs hadn't tried to exterminate them)
The highest populations of Muslims can be found in the middle east and Asia. The northern parts of Africa are also known to have a large number of Muslims.
Southwestern Asia
Indonesia
Afghanistan is the country with the highest percentage of Muslim population.
Pakistan (174 millions Muslims population) is the second to Indonesia (203 millions Muslims population) in having the highest Muslims population.
Northern Africa (just answered in apex)
Iran.
The country which has the highest percentage of Catholics is the Vatican City - the percentage is at 100!
christianity
Asia has the highest percentage of the world's population. The next highest is North America and then Europe. Antarctica is the least populated continent.
united states
Kerala
Argentina
The percentage of the population in Canada that is estimated to be agnostic is 16.2%. It is a big percentage if we compare it to some other countries but still not the highest.
Indonesia is the country with highest number of Muslim population (over 200 million)