How many times is the density of the nucleus more than the density of water ?

In helium nucleus, there are

What kind of a force does neutron-neutron ?

Explain isotopes, isobar, isotones and isomers by giving examples. 

From the relation $R=R_{0} A^{1 / 3},$ where $R_{0}$ is a constant and $A$ is the mass number of a nucleus, show that the nuclear matter density is nearly constant (i.e. independent of $A$).