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0 is reserved for long-distance calls and cannot be used as a local initial digit (see below). 901 to 909 have been reserved for automated system of national collect calls ( see below) since 1982 and cannot be used a local initial digits. 900 was used to premium-rate telephone numbers in the 1990s, but is not in use now.
Thus, it is strongly recommended that telephone numbers should be stored in mobile phones in the form of the full international number, should the owner of the phone be likely to use the phone concerned in an area away from home, either within Australia or internationally.
When calling France from abroad, the leading zero should be omitted: for example, to call a number in Southwest France, one would dial +33 5 xx xx xx xx. French people usually state phone numbers as a sequence of five double-digit numbers, e.g., 0x xx xx xx xx (and not, for example, 0 xxx-xxx-xxx or 0xxx-xx-xxxx or 0xx-xxx-xxxx).
Wall–Sun–Sun prime. Waring–Goldbach problem. Waring's problem. Wieferich prime. Wilson prime. Wolstenholme prime. Woodall number. Categories: Unsolved problems in mathematics.
German tank problem. During World War II, production of German tanks such as the Panther was accurately estimated by Allied intelligence using statistical methods. In the statistical theory of estimation, the German tank problem consists of estimating the maximum of a discrete uniform distribution from sampling without replacement.
Country calling codes, country dial-in codes, international subscriber dialing ( ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks. Country codes are defined by the International Telecommunication Union (ITU) in ITU-T standards E.123 and E.164. The ...
411 (telephone number) 411 is a telephone number for local directory assistance in Canada and the United States. Until the early 1980s, 411 – and the related 113 number – were free to call in most jurisdictions. In the United States, the service is commonly known as "information", [1] although its official name is "directory assistance".
Heesch's problem is the problem of determining the set of numbers that can be Heesch numbers. Both are named for geometer Heinrich Heesch, [1] who found a tile with Heesch number 1 (the union of a square, equilateral triangle, and 30-60-90 right triangle) [2] and proposed the more general problem.