It is mentioned here that the public value $N=p*q$ of the RSA cryptosystem can be factorized if one of the factors is reused. Thus, if $N_1=p*q_1$ and $N_2=p*q_2$ and only $N_1$ and $N_2$ are known, then one can factor $N_1$ and $N_2$.
I wasn't able to come up how this can be achieved. Is that statement really true?