This is contained in a Muslim publication, The Muslim 500 in its 2018 edition.
The publication noted that there were approximately 1.84 billion Muslims in the world, making up 24.38 per cent of the world’s population.
Last year, the trio also made the list of most influential Muslims in the world.
Buhari and the Sultan were ranked 19th and 23th, respectively among the first top 50 Muslims in the world.
It explained that Shekau, the head of Boko Haram, a terrorist group in Nigeria had carried out a number of atrocities.
The publication added that Shekau speaks Hausa, Arabic, and English and claimed to have undergone theological training.
Others Nigerians listed in the publication are Africa’s richest man, Aliko Dangote; JAMB registrar, Prof. Ishaq Oloyede and former justice minister, Prince Bola Ajibola.