With Harry Potter and the Deathly Hallows due for release at midnight on Friday, we look at some of the key numbers behind this publishing phenomenon.

The author: JK Rowling

£2,500 – The original advance from Bloomsbury for Harry Potter and the Philosopher's Stone.

£545m – Her estimated fortune. This made her the 13th wealthiest British woman, on this year's Sunday Times Rich List.

£50m – The estimated earnings of Christopher Little, Ms Rowling's agent.

The publisher: Bloomsbury

£13.71m – Its annual turnover in 1997, the year Harry Potter and the Philosopher's Stone was published.

£109.1m – Its annual turnover eight years later, boosted by publication of the eagerly awaited sixth book.

74% - The drop in Bloomsbury's profits in 2006, when it didn't have a new Potter to publish.

50% - The drop in the company's share price since summer 2005, as investors have adjusted to life after Potter.

£10m – Estimated cost of the worldwide security operation ahead of the publication of Deathly Hallows.

The books

325m – The number of Harry Potter books sold worldwide (excluding pre-orders for Deathly Hallows).

1.8m – Amazon's pre-orders for Deathly Hallows, an all-time record.

£27,000 – The price raised by a signed first edition of Harry Potter and the Goblet of Fire, sold at auction by JK Rowling's father.

£17.99 – The recommended retail price for Deathly Hallows.

£5 – The cheapest price it will be available for in the UK.

The films

$140m – The first five day's US box office takings for Harry Potter and the Order of the Phoenix.

$3.5bn – Warner Brothers' combined takings from the first four movies.

The stars

£17m – Daniel Radcliffe's fortune, as calculated by the Sunday Times Rich List 2007.

£5m – Estimated earnings of co-stars Emma Watson and Rupert Grint, each.