61

This number is a prime.

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When numbering the sixty vertices of the fullerine buckyball in ordered pairs of ascending and descending numbers, the sum of the opposite pairs will equal 61. [McGown]

In 1838, astronomer Friedrich Wilhelm Bessel calculated the large proper motion of 61 Cygni using trigonometric parallax. This was the first star (other than the Sun) to have its distance known from the Earth. [McGown]