Nicomachus's Introduction to Arithmetic set out the properties of numbers, including the earliest surviving Greek multiplication table, classifying numbers as perfect, deficient, abundant, triangular, square and by other categories in a framework that treated arithmetic and number mysticism as inseparable rather than as separate subjects. For Nicomachus, as for the Pythagorean tradition he claimed to represent, a number's mathematical properties and its symbolic or religious meaning were the same subject studied from two angles, not two different disciplines.
That fusion of mathematics and number symbolism is the direct ancestor of what later became the distinct, non mathematical practice of numerology, though Nicomachus's own work remains genuine ancient mathematics rather than the fortune telling application of number meanings that developed centuries later under writers such as L. Dow Balliett. The atlas records Introduction to Arithmetic as the foundational Neopythagorean text it is, the point at which rigorous number theory and symbolic number meaning were still a single unified study, before the two later diverged into separate mathematical and occult traditions.
Boethius later adapted Nicomachus's material into Latin for his own De Institutione Arithmetica, cementing the work's place at the head of the medieval quadrivium, the four mathematical arts of arithmetic, geometry, music and astronomy that structured higher education in Europe for centuries after Nicomachus himself had been largely forgotten as an individual author.