SB 4.9.22
Devanāgarī
प्रस्थिते तु वनं पित्रा दत्त्वा गां धर्मसंश्रय: । षट्-त्रिंशद्वर्षसाहस्रं रक्षिताव्याहतेन्द्रिय: ॥ २२ ॥
Text
prasthite tu vanaṁ pitrā dattvā gāṁ dharma-saṁśrayaḥ ṣaṭ-triṁśad-varṣa-sāhasraṁ rakṣitāvyāhatendriyaḥ
Synonyms
prasthite—after departure;tu—but;vanam—to the forest;pitrā—by your father;dattvā—awarding;gām—the whole world;dharma-saṁśrayaḥ—under the protection of piety;ṣaṭ-triṁśat—thirty-six;varṣa—years;sāhasram—one thousand;rakṣitā—you will rule;avyāhata—without decay;indriyaḥ—the power of the senses.
Translation
After your father goes to the forest and awards you the rule of his kingdom, you will rule continuously the entire world for thirty-six thousand years, and all your senses will continue to be as strong as they are now. You will never become old.
Purport
In the Satya-yuga people generally lived for one hundred thousand years. Dhruva Mahārāja’s ruling the world for thirty-six thousand years was quite possible in those days.