### Counting Factors

Is there an efficient way to work out how many factors a large number has?

### Big Powers

Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.

### Dozens

Can you select the missing digit(s) to find the largest multiple?

# Powerful Finale

##### Age 11 to 14 ShortChallenge Level

What is the last digit of $3^{2011}$?

If you liked this problem, here is an NRICH task that challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.