The article studies the structural components of the composition and architectonics of Vyacheslav Ivanov’s lyrical book Rosarium that is part of Cor Ardens from the point of view of numeral symbolism. Special attention is paid to the analysis of the category of number in the poet’s philosophy and the poetics of Cor Ardens. The author studies the symbol of the rose and its numeral aspects, central to Rosarium along with the development of the aforementioned symbol in the poetics of Cor Ardens. With reference to the symbol of the rose, the article studies the gradual development of the symbol into an archetype that includes numeral symbols, and the attainment through this archetype of the theurgical function of poetry crucial for Ivanov’s creative work.