Those Fascinating Numbers 187
11 715
the
19th
solution of φ(n) = φ(n + 1) (see the number 15).
11 872
the number of Niven numbers 105 (see the number 213).
11 881 (=
1092)
the smallest five digit perfect square which has only two distinct digits (see the
number 1 444);
the second star number 1 which is also a perfect square (see the number
121).
11 907
the seventh odd number n 1 such that γ(n)|σ(n) (see the number 135).
11 935
the third solution of σ(n) = σ(n + 3) (see the number 382).
12 008
the ninth dihedral perfect number (see the number 130).
12 025
the fifth number whose square can be written as the sum of three fourth powers:
12
0252
=
604
+
754
+
1004
(see the number 481).
12 101
the smallest five digit prime number whose digits are consecutive (see the num-
ber 67).
12 167
the fifth powerful number n such that n + 1 is also powerful (see the number
288): here 12 167 =
233
and 12 168 =
23
·
32
·
132.
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