Thursday, September 17, 2009

681

681 = 3 x 227.

The sum of the digits of 681 is five times the number of digits: 6 + 8 + 1 = 15 = 3 x 5.

681 is the sum of 11 positive 5th powers: 681 = 35 + 35 + 25 + 25 + 25 + 25 + 25 + 25 + 15 + 15 + 15.


681 is a centered pentagonal number.


The galaxy NGC 681, more than 55 million light years away, resembles the striking Sombrero Galaxy (M104).

Source: Wolfram MathWorld

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