During his five year stay in Cambridge, Ramanujan published twenty one research papers containing theorems on definite integral, modular equations, Riemann’s zeta function, infinite series, summation of series, analytic number theory, asymptotic formulae, modular functions, partitions and combinatorial analysis. His paper entitled Highly Composite Numbers which appeared in the Journal of the London Mathematical Society, in 1915, is 62 pages long and contains 269 equations. This is his longest paper. The London Mathematical Society has some financial difficulties at that time and Ramanujan was requested to reduce the length of his paper to save printing expenses. Five of these 21 research papers were in collaboration with Hardy. Ramanujan also published five short notes in the Records of Proceedings at meetings of the London Mathematical Society and six more in the journal of the Indian Mathematical Society.