1. Find the number of pairs (m, n) such that 2(adsbygoogle = window.adsbygoogle || []).push({}); ^{m}- 2^{n}= 63 in which m and n are nonnegative integers.

2. What is the units digit of 6^{25}- 3^{24}?

3. How many perfect squares divide the number 4!*5!*6! ?

4. What is the last digit of the sum 1! + 2! + 3! + ... + 2010! + 2011! ?

Thanks!

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# A few questions

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