Somehow, it seems speedcrunch has a problem in dealing with big numbers. For example, I can do:

(3(7^204+7^202+7^200)+7(3^204+3^200)-210) mod 10

in the calculator that comes with linux and get the right result (which is 7), but speedcrunch overflows and outputs 0. I've set the result format to fixed decimal and precision to 50 digits, but that doesn't seem to make a difference.

Edit: Just tried it with insect, which also gets it wrong.