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Forty-five (45, XLV) is the natural number following forty-four and followed by forty-six. It is a triangular number.

Its divisors are 3, 9, 15 and 45. Its prime factorization is

See also: forty
45 is also:

Originally the 45 RPM record was introduced as a longer play version of the 78 RPM discs. The first 45 RPM records were monaural with recordings on both sides of the Disc. Produced in several sizes, the 7" large hole version became the most popular. As stereo recordings became popular in the 1950s, most all of the newer 45 RPM records were recorded in Stereo.

See: 78, LP and 33.