In Genesis's Noah's Ark account, Noah was 601 years old when the ground became completely dry.
Genesis 8:13 says that in Noah's 601st year, on the first day of the first month, he removed the Ark's covering and saw that the surface of the ground was dry. A later verse states that the earth was completely dry by the 27th day of the second month, when God told Noah to leave.
This age is easy to confuse with the earlier statement that Noah was 600 years old when the Flood began. The narrative moves from the beginning of the Flood during his 600th year to the drying of the earth during his 601st year.
The age markers help Genesis present the episode as a dated sequence. They distinguish the start of the Flood, the recession of the waters, and the final departure from the Ark.