What's the smallest number with four different prime factors?

Add to your resource collection Remove from your resource collection Add notes to this resource View your notes for this resource

\(f(x)\) denotes the number of different prime factors of the integer \(x\), excluding \(1\) and \(x\) itself. For example, since \(12=2\times2\times3\), then \(f(12)=2\).

1. Calculate \(f(121)\).
2. Calculate \(f(17)\).
3. Write down the smallest \(x\) for which \(f(x)=4\).