Within positive integers, 2. If negative integers are permitted, 2 and 2. In the complex domain, 2, 2, 2i and 2i (where i is the imaginary square root of 1)
http://wiki.answers.com/Q/What_is_the_fourth_root_...

The answer is 6. Hope this helps.
http://www.chacha.com/question/whatisthecomplex...

sqrt(2)+i*sqrt(2), sqrt(2)+i*sqrt(2), sqrt(2)i*sqrt(2), sqrt(2)i*sqrt(2)
http://answers.yahoo.com/question/index?qid=200906...

1. Enter the number whose fourth root you want to calculate. With this example, enter "625. 2. Press the calculator's square root button, which has the "√" symbol
http://www.ehow.com/how_8152033_calculatefourthr...
