The love for the study of magic squares and amicable numbers led Muslims to develop the theory of numbers. Al-Khujandi discovered a particular case of Fermat's theorem that "the sum of two cubes cannot be another cube", while alKaraji analyzed arithmetic and geometric progressions such as: 1^3+2^3+3^3+...+n^3=( 1+2+3+...+n)^2.
Al-Biruni also dealt with progressions while Ghiyath al-Din Jamshid al-Kashani brought the study of number theory among Muslims to its peak.