11

11 November is Armistice Day / Remembrance Day, observed in the United Kingdom, Commonwealth countries, France and Belgium; marked as Veterans Day in the United States. The armistice ending fighting on the Western Front took effect at 11am on 11 November 1918 — the eleventh hour of the eleventh day of the eleventh month. A two-minute silence at 11am is observed in the UK and Commonwealth. The United States renamed its observance Veterans Day in 1954.

Western numerology assigns eleven the status of a master number, left unreduced rather than added to two. The master numbers are the exception to numerology's central operation of reducing to a single digit. Practitioner sources describe them as intensified rather than merely larger; the exemption is a convention of the system, with no arithmetic behind it. This is a modern popular interpretation, not a historical or doctrinal claim.

Presented as belief or tradition, not as an established fact.

There are about 11 kilometres of depth at the deepest point of the ocean (Challenger Deep, the Mariana Trench). Close to 10,935 metres, which is deeper than Everest is tall. Four crewed descents had reached it by 2019, against twelve people who have walked on the Moon.

The depth of the Challenger Deep in the Mariana Trench is about 11 kilometres (western Pacific). The figure varies by tens of metres between surveys. Deeper below sea level than Everest is above it, by more than two kilometres.

The annual rainfall at Mawsynram in Meghalaya is about 11 thousand millimetres (north-east India). Around fifteen times London's. Almost all of it falls in the monsoon months, when moist air off the Bay of Bengal is forced up against the hills.

Whether a number divides by 11 can be settled by adding and subtracting its digits alternately: 918,082 gives 9 − 1 + 8 − 0 + 8 − 2 = 22, which is a multiple of 11, so the whole number is. The test works because powers of ten alternate between one more and one less than a multiple of 11, so each digit's contribution flips sign.

A standard football (soccer) team and a standard cricket team each field 11 players on the pitch at once — one of the most widely recognised team sizes in world sport.

11 is the atomic number of sodium. Bound to chlorine it forms common table salt, and sodium ions carry the electrical signals along human nerves. Burning sodium gives the yellow-orange of older street lighting.