What numerical identities and facts remain true when the page is rotated 180 degrees ("strobogrammatic")?

arithmetic/digits/strobogrammatic New

New entry, edited from material collected for the archive and not yet in a released version.

Problem

What numerical identities and facts remain true when the page is rotated
180 degrees ("strobogrammatic")?

[ Editor: problem statement reconstructed from the postings. ]

Show solution

1/.  Date:  9.6.96  =  96  x  101

     Strobogrammatic,  Rotate page 180 degrees.

     96  =

     625 -529
     still Strobogrammatic

     = | 25^2 - 23^2  | .
     still Strobogrammatic.       (Except 3E,  ^ .)

    The equation (digits pattern) is substantially true if the page
        is rotated through 180 degrees.  " Strobogrammatic."

#         STROBOGRAMMATIC PRIME is a prime   which
#         when turned upside-down is
# still a prime.  If it is not a palindrome, then it is one
# of a pair of two distinct primes, like the
# strobogrammatic pair of primes 199 and 661.

# gopher:
//gopher.utm.edu/00/user/Public_FTP/pub/math/primes/types.txt

2/.  Number of days in a quarter.

     91_5/16 = 365.25/4 days. Quarter. Strobogrammatic.
                              Rotate page 180 degrees.

3/.    Jesus has turned my life <umop ap!sdn>.

-- Don McDonald <don.mcdonald@welcom.gen.nz>, Wellington, New Zealand,
   June 1996