138 (number)
138 (one hundred ndthirty-eight) is the natural number following 137 and preceding 139. In mathematics 138 is a sphenic number, the sum of four consecutive primes (29 + 31 + 37 + 41), and the smallest product of three primes, such that in base 10, the third prime is a concatenation of the other two: 2 \cdot 3 \cdot 23. 138 is the third 47- gonal number and an Ulam number, as well as a one step palindrome (138 + 831 = 969.) 138 is the 72nd normal congruent number and the 49th primitive or square free congruent number. In astronomy * 138 Tolosa is a brightly colored, stony main belt asteroid * The New General Catalogue object NGC-138, a spiral galaxy in the constellation Pisces * The Saros number of the solar eclipse series which began on June 6, 1472 and will end on July 11, 2716. The duration of Saros series 138 is 1244 years, and it contains 70 solar eclipses * 138P/Shoemaker-Levy is a periodic comet in the Solar System In the military * United States Air Force 138t ...
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