# 168809

This number is a composite.

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The smallest invertible Sophie Germain semiprime n,
containing all of the invertible digits that yields a
different Sophie Germain semiprime m when rotated by 180
degrees. As such, {n, (2*n+1)}; {m, (2*m+1)}, i.e.,
{168809, 337619} and {608891, 1217783} all are semiprime.
Curiously, n is also expressible as the sum of two squares
in two different ways: (80^2 + 403^2) and (220^2 + 347^2). [Bajpai]
Submitted: 2018-12-14 14:29:21; Last Modified: 2018-12-14 17:02:34.

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