In the Philosopher's Stone, we read a passage from a library book giving Flamel's age as 665:
Mr Flamel, who celebrated his six hundred and sixty-fifth birthday last year, enjoys a quiet life in Devon with his wife, Perenelle (six hundred and fifty-eight).
Harry Potter and the Philosopher's Stone - p.161 - Bloomsbury - Chapter 13, Nicolas Flamel
Which I always took to be his age during the events of the Philosopher's Stone.
But it occurred to me today that this information came from a very old library book and is surely out of date:
Harry and Ron barely had time to exchange mystified looks before she was dashing back, an enormous old book in her arms.
Harry Potter and the Philosopher's Stone - p.160 - Bloomsbury - Chapter 13, Nicolas Flamel
So how old was he really? Has Rowling ever said? Because it occurs to me that an author would not have written that passage except to give the audience an indication of his age.