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Number

$728$ (seven hundred and twenty-eight) is:

$2^3 \times 7 \times 13$

The $1$st positive integer which can be expressed as the sum of $2$ cubes in $3$ different ways:

$728 = 6^3 + 8^3 = \paren {-1}^3 + 9^3 = \paren {-10}^3 + 12^3$

The smaller of the $1$st pair of Smith brothers:

$7 + 2 + 8 = 2 + 2 + 2 + 7 + 1 + 3 = 17$, $7 + 2 + 9 = 3 + 3 + 3 + 3 + 3 + 3 = 18$

The $37$th Smith number after $4$, $22$, $27$, $58$, $\ldots$, $576$, $588$, $627$, $634$, $636$, $645$, $648$, $654$, $663$, $666$, $690$, $706$:

$7 + 2 + 8 = 2 + 2 + 2 + 7 + 1 + 3 = 17$

Also see

• Previous  ... Next: Smith Number
• Next: Smith Brothers
• Next: Integer as Sum of 2 Cubes in 3 Ways

Sources

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $728$