Ibn Tahir Al-Baghdadi
Al-Baghdadi was born in 980 in Baghdad and was a polymath in Islamic society. He studied and taught Islamic jurisprudence from the Shafi’i school of thought, one of the four schools of legal thought in Sunni Islam, and was a jurist, specializing in inheritance law . Further, he was interested in arithmetic and number theory, having produced two books: Kitab fi’l-misaha, or The Book in Measurements, and al-Takmila fi’l Hisab, or The Completion in Arithmetic. He may have been the first in history to study equivalent numbers in detail.
Introduction to Equivalent Numbers
Equivalent numbers are numbers such that the sum of their proper divisors are equal. For instance, 159 and 559 are proper divisors, since the proper divisors of 159 and 559 both sum to 57:
go (159) = 1+3+53 = 57
= do (559) 1+13+ 43 = 57.
We now turn our attention to Al-Baghdadi, whose brilliance will be shown soon.