Number 10, often referred to as 10 Downing Street, is the official residence and executive office of the Prime Minister of the United Kingdom. Located in London, it has been the home of British Prime Ministers since 1735. The building is known for its distinctive black door and is a symbol of the UK government. The number 10 is also significant in mathematics, representing a base in the decimal system. It is the first two-digit number and is often associated with completeness, as it follows the single digits from 0 to 9.