Number:15 (Meta, no ontology)
From Compile Worlds
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| - | '''15''' is the first [[magic number]] which is not also a [[prime number]]. However, this is because 15 = 2<sup>4</sup>-1, and the exponent 4 is not prime. The first magic number whose exponent is | + | '''15''' is the first [[magic number]] which is not also a [[prime number]]. However, this is because 15 = 2<sup>4</sup>-1, and the exponent 4 is not prime. The first non-prime magic number whose exponent is itself prime is in fact 2<sup>11</sup>-1 = [[2,047]] = [[23]] × [[89]]. |
| - | 15 is also the third [[tetramagic number]], and the last which is small enough to [[care]] about, as the fourth is [[ | + | 15 is also the third [[tetramagic number]], and the last which is small enough to [[care]] about, as the fourth is [[65,535]] and the fifth is [[way too freaking big]] to write here. |
{{Numbers|Magic numbers}} | {{Numbers|Magic numbers}} | ||
Latest revision as of 17:07, 26 April 2009
15 is the first magic number which is not also a prime number. However, this is because 15 = 24-1, and the exponent 4 is not prime. The first non-prime magic number whose exponent is itself prime is in fact 211-1 = 2,047 = 23 × 89.
15 is also the third tetramagic number, and the last which is small enough to care about, as the fourth is 65,535 and the fifth is way too freaking big to write here.
