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MATHEMATICS
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There are just
four numbers (after 1) which are the sums of the cubes of their
digits:
153 = 1^3 + 5^3 + 3^3
370 = 3^3 + 7^3 + 0^3
371 = 3^3 + 7^3 + 1^3 and
407 = 4^3 + 0^3 + 7^3 |
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The prime number
73,939,133 has a very strange property. If you keep removing a digit
from the right hand end of the number, each of the remaining numbers
is also prime. It's the largest number known with this property.
Take a look: 73,939,133 and 73,939,13 and 73,939,1 and 73,939 and
7,393 and 739 and 73 and 7 are all prime! |
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12+3-4+5+67+8+9=100 |
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The factors of 28 (not including itself) are 1, 2, 4, 7 and 14 and 1
+ 2 + 4 + 7 + 14 = 28 |
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1x9 + 2 = 11
12x9 + 3 = 111
123x9 + 4 = 1111 |
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