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Number | Why is it interesting? |
$2$ | It is the smallest prime. |
$28$ | A perfect number: it is equal to the sum of its proper factors: $28 = 1+2+4+7+14$. |
$100$ | $100=2^2$ in binary, $100=3^2$ in base $3$, $100=10^2$ in base $10$ and $100=n^2$ in base $n$ |
$230$ | The total number of different symmetry structures crystals in three dimensions can exhibit. |
$541$ | The hundredth prime number . |
$1089$ | Take any 3 digit number whose digits are not all the same, reverse it and subtract from the first, take the new number and add its reverse. This will equals $1089$. |
$1729$ | The smallest number expressible as the sum of two cubes in two different ways. |
$1999$ | The smallest prime number such that the sum of its digits is a perfect number. |
$2^{43112609}-1$ | The largest prime number known in $2008$. |