Are there any trillionaire companies in the world?

Could you elaborate on the current state of affairs regarding trillionaire companies in the global landscape? Are there any corporations or entities that have surpassed the monumental milestone of reaching a trillion-dollar valuation? If so, which ones stand out and what factors have contributed to their extraordinary success? On the other hand, if none exist, what are the primary challenges or obstacles that hinder companies from attaining such a lofty financial achievement?