Ottoman Empire:

By contrast, the Habsburg frontier had settled somewhat, a stalemate caused by a stiffening of the Habsburg defences. The Long War against Habsburg Austria (15931606) created the need for greater numbers of Ottoman infantry equipped with firearms, resulting in a relaxation of recruitment policy. This contributed to problems of indiscipline and outright rebelliousness within the corps, which were never fully solved. Irregular sharpshooters (Sekban) were also recruited, and on demobilization turned to brigandage in the Jelali revolts (15951610), which engendered widespread anarchy in Anatolia in the late 16th and early 17th centuries. With the Empire's population reaching 30 million people by 1600, the shortage of land placed further pressure on the government . In spite of these problems, the Ottoman state remained strong, and its army did not collapse or suffer crushing defeats. The only exceptions were campaigns against the Safavid dynasty of Persia, where many of the Ottoman eastern provinces were lost, some permanently. This 16031618 war eventually resulted in the Treaty of Nasuh Pasha, which ceded the entire Caucasus, except westernmost Georgia, back into Iranian Safavid possession. Campaigns during this era became increasingly inconclusive, even against weaker states with much smaller forces, such as Poland or Austria.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What was the population of the Ottoman empire at the beginning of the 17th century?
30 million people