Here are the top 10 and bottom 10 Muslim majority countries by literacy rate with their associated population numbers:
Top 10:
Kazakhstan - 99.8% (18.8 million)
Azerbaijan - 99.8% (10.1 million)
Turkmenistan - 99.7% (6.0 million)
Tajikistan - 99.7% (9.5 million)
Kyrgyzstan - 99.5% (6.6 million)
Uzbekistan - 99.4% (33.9 million)
Brunei - 96.7% (0.4 million)
Iran - 97.6% (84.7 million)
Qatar - 96.3% (2.9 million)
Indonesia - 95.4% (274.9 million)
Bottom 10:
Mali - 35.5% (20.3 million)
Burkina Faso - 41.4% (21.5 million)
Niger - 42.9% (24.2 million)
Guinea - 45.6% (13.5 million)
Sierra Leone - 48.5% (8.1 million)
Chad - 49.6% (16.9 million)
Afghanistan - 52.2% (39.8 million)
Mauritania - 57.5% (4.7 million)
Pakistan - 59.1% (225.2 million)
Senegal - 61.9% (16.7 million)