Given: f:N−1→N
f(n)= The highest prime factor of n.
Since, the only prime factor of 2 is 2.
⇒f(2)=2
Also, factors of 4 are 1,2and4. Out of these, the highest prime factor is 2.
⇒f(4)=2
Similarly the highest prime factor of 16,32,64,128,... is 2
So, the given function is many one.
Now, no composite number will be image of any number.
Example: 4 is not image of any element
So, the given function f(x) is into.
Hence many one and into
Or, neither one-one nor onto.