Genesis is full of patterns that are intended to draw your attention; breaks in the repetition should make you stop and ask, "Why?"
Genesis 5 lists the ages in the generations between Adam and Noah, and a few stand out. The youngest, the oldest, and the one with the strange number.
Methuselah lived the longest – 969 years. His name is linked to his long life, which was not just for his benefit, but for the benefit of humanity as God restrained the Flood until after Methuselah died.
Enoch notably never died.
And Lamech? He shares a name with a notable man in Cain's genealogy. Cain's Lamech is man of seventy-seven-fold vengeance. But the Lamech of Genesis 5 goes down a different path. Not one of vengeance, but of Comfort.