29 Arlington Avenue is a house in Islington, London. Douglas Adams shared the house for a time with Jonny Brock and Clare Gorst. It is mentioned in the dedication of The Hitchhiker's Guide to the Galaxy, which is dedicated to the "Arlingtonians for tea, sympathy, and a sofa."
The phone number of this house was 226 7709. In The Hitchhiker's Guide to the Galaxy when Arthur Dent and Ford Prefect are rescued in ZZ9 Plural Z Alpha, the probability of that happening was 2 to the power of 267,709 to one against.