The exact number of women of Jannah (hūr al-'Aīn, Arabic: حور العين) is unknown. There are several hadiths on the topic, but only a handful are graded sahih (authentic).
The following hadith says everyone in Jannah will get two wives:
عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَوَّلُ زُمْرَةٍ تَلِجُ الْجَنَّةَ صُورَتُهُمْ عَلَى صُورَةِ الْقَمَرِ لَيْلَةَ الْبَدْرِ، لاَ يَبْصُقُونَ فِيهَا وَلاَ يَمْتَخِطُونَ وَلاَ يَتَغَوَّطُونَ، آنِيَتُهُمْ فِيهَا الذَّهَبُ، أَمْشَاطُهُمْ مِنَ الذَّهَبِ وَالْفِضَّةِ، وَمَجَامِرُهُمُ الأَلُوَّةُ، وَرَشْحُهُمُ الْمِسْكُ، وَلِكُلِّ وَاحِدٍ مِنْهُمْ زَوْجَتَانِ، يُرَى مُخُّ سُوقِهِمَا مِنْ وَرَاءِ اللَّحْمِ، مِنَ الْحُسْنِ، لاَ اخْتِلاَفَ بَيْنَهُمْ وَلاَ تَبَاغُضَ، قُلُوبُهُمْ قَلْبٌ وَاحِدٌ، يُسَبِّحُونَ اللَّهَ بُكْرَةً وَعَشِيًّا
Narrated Abu Huraira: Allah's Messenger (ﷺ) said, "The first group (of people) who will enter Paradise will be (glittering) like the moon when it is full. They will not spit or blow their noses or relieve nature. Their utensils will be of gold and their combs of gold and silver; in their centers, the aloe wood will be used, and their sweat will smell like musk. Everyone of them will have two wives; the marrow of the bones of the wives' legs will be seen through the flesh out of excessive beauty. They ( i.e. the people of Paradise) will neither have differences nor hatred amongst themselves; their hearts will be as if one heart and they will be glorifying Allah in the morning and in the evening."
— Sahih al-Bukhari, Book 59, Hadith 56
In 'Umdat al-Qārī, Vol. 15, pp. 154-155, Badr al-Din al-Ayni explained that At-Tayyibi said that the two wives are from the women of this world. This, however, was disputed by other scholars as there is another hadith in Sahih al-Bukhari (Book 59, Hadith 64) that stipulates said women to be of hūr al-'Aīn. Scholars agree, though, that the number two is not for specificity, but rather for enumeration, i.e., two or more (Arabic: للتكرير لَا للتحديد). This literary device is quite common in the Arabic language (e.g., the use of karratayn in Surat Al-Mulk 67:4). Ibn Qayyim al-Jawziyya, and of course Imam Ahmad ibn Hanbal, mentioned that the number of hūr al-'Aīn, albeit unknown, will definitely be more than two based on this hadith:
عَنْ أَبِي بَكْرِ بْنِ عَبْدِ اللَّهِ بْنِ قَيْسٍ، عَنْ أَبِيهِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ : إِنَّ لِلْمُؤْمِنِ فِي الْجَنَّةِ لَخَيْمَةً مِنْ لُؤْلُؤَةٍ وَاحِدَةٍ مُجَوَّفَةٍ طُولُهَا سِتُّونَ مِيلاً لِلْمُؤْمِنِ فِيهَا أَهْلُونَ يَطُوفُ عَلَيْهِمُ الْمُؤْمِنُ فَلاَ يَرَى بَعْضُهُمْ بَعْضًا
Abu Bakr b. Abdullah b. Qais reported on the authority of his father that Allah's Messenger (ﷺ) said that in Paradise there would be for a believer a tent of a single hollowed pearl the breadth of which would be sixty miles. It would be meant for a believer and the believers would go around it and none would be able to see the others.
— Sahih Muslim, Book 53, Hadith 27
Apart from the above, there is no other mention in authentic hadiths of the number of hūr al-'Aīn. There are hadiths that specify 72 for the martyrs (see Jami' at-Tirmidhi 22/46/1663 and Sunan Ibn Majah 4/24/2799), but these hadiths are graded hassan at best.
