"Prohibited to you (For marriage) are:- Your mothers, daughters, sisters; father's sisters, Mother's sisters; brother's daughters, sister's daughters; foster-mothers (Who gave you suck), foster-sisters; your wives' mothers; your step-daughters under your guardianship, born of your wives to whom ye have gone in,- no prohibition if ye have not gone in;- (Those who have been) wives of your sons proceeding from your loins; and two sisters in wedlock at one and the same time, except for what is past; for Allah is Oft-forgiving, Most Merciful;" - Quran 4:23 (read more)

"Narrated Qatada: Anas bin Malik said, "The Prophet used to visit all his wives in a round, during the day and night and they were eleven in number." I asked Anas, "Had the Prophet the strength for it?" Anas replied, "We used to say that the Prophet was given the strength of thirty (men)." And Sa'id said on the authority of Qatada that Anas had told him about nine wives only (not eleven)." - Sahih Bukhari 1:5:268 (read more)

"This marriage of yours [to an atheist] is invalid and it is not permissible to allow him to be intimate with you unless he comes back to Islam and enters the faith by pronouncing the Shahaadatayn and following the rulings of Islam. If he does not do that then the marriage must be annulled in a sharee’ah court." - Islam Q&A