 Highly Composite Numbers by Srinivasa Ramanujan

Primary article text: ramanujan.sirinudi.org/Volumes/published/ram15.pdf . Proceedings of the London Mathematical Society (2) 14, 347–409. Sections 1–8 define record values of the divisor function and describe the prime-exponent structure. The available text is a retypesetting of the original, with editorial remarks distinguished from Ramanujan’s text.