Friday 9 October 2009

Numbers with an odd number of factors

We saw in the session that:

Prime numbers only have two factors {1 and itself}

eg

2 has {1,2}
3 has {1, 3}
5 has {1, 5}

Some numbers have an odd number of factors:
1 only has one factor {1}
4 has {1, 2, 4}
9 has three factors {1, 3, 9}

Can you find any other numbers with an odd number of factors?
What do these numbers have in common?

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