﴿ وَمَا جَعَلْنَآ أَصْحَٰبَ ٱلنَّارِ إِلَّا مَلَٰٓئِكَةًۭ ۙ وَمَا جَعَلْنَا عِدَّتَهُمْ إِلَّا فِتْنَةًۭ لِّلَّذِينَ كَفَرُوا۟ لِيَسْتَيْقِنَ ٱلَّذِينَ أُوتُوا۟ ٱلْكِتَٰبَ وَيَزْدَادَ ٱلَّذِينَ ءَامَنُوٓا۟ إِيمَٰنًۭا ۙ وَلَا يَرْتَابَ ٱلَّذِينَ أُوتُوا۟ ٱلْكِتَٰبَ وَٱلْمُؤْمِنُونَ ۙ وَلِيَقُولَ ٱلَّذِينَ فِى قُلُوبِهِم مَّرَضٌۭ وَٱلْكَٰفِرُونَ مَاذَآ أَرَادَ ٱللَّهُ بِهَٰذَا مَثَلًۭا ۚ كَذَٰلِكَ يُضِلُّ ٱللَّهُ مَن يَشَآءُ وَيَهْدِى مَن يَشَآءُ ۚ وَمَا يَعْلَمُ جُنُودَ رَبِّكَ إِلَّا هُوَ ۚ وَمَا هِىَ إِلَّا ذِكْرَىٰ لِلْبَشَرِ ﴾

“For We have caused none but angelic powers to lord over the fire [of hell]; and We have not caused their number to be aught but a trial for those who are bent on denying the truth - to the end that they who have been granted revelation aforetime might be convinced [of the truth of this divine writ]; and that they who have attained to faith [in it] might grow yet more firm in their faith; and that [both] they who have been granted the earlier revelation and they who believe [in this one] might be freed of all doubt; and that they in whose hearts is disease and the who deny the truth outright might ask, "What does [your] God mean by this parable?" In this way God lets go astray him that wills [to go astray], and guides aright him that wills [to be guided]. And none can comprehend thy Sustainers forces save Him alone: and all this is but a reminder to mortal man.”

The conditions of hell described in the Quran relate to the unseen and hidden world. There being nineteen angels in hell is also a fact of a similar nature. If one resorts to hair-splitting, these matters will only increase one’s doubts. But if the way of complete faith is adopted, these matters will increase one’s fear of the Hereafter.