Those Fascinating Numbers 295
9 694 845
the
15th
Catalan number (see the number 14).
9 745 728
the
13th
number n such that φ(n) + σ(n) = 3n (see the number 312).
9 800 817
the third number n 1 which can be written as the sum of the seventh powers
of its digits (see the number 1 741 725).
9 841 094
the second number n such that P
(n)2|n,
P (n +
1)2|n
+ 1 and P (n +
2)2|n
+ 2:
here 9 841 094 =
2·67·2712,
9 841 095 =
34 ·5·11·472
and 9 841 096 =
23 ·17·2692
(see the number 1 294 298).
9 876 413
the largest prime number made up of exactly seven distinct digits (see the
number 9 871).
9 926 315
the fourth number n 1 which can be written as the sum of the seventh powers
of its digits (see the number 1 741 725).
9 980 583
the fifth number n such that
n2
+ 2 is powerful: here
9 980
5832
+ 2 = 99612037019891 =
113
·
2735692
(see the number 265).
9 999 991
the largest seven digit prime number.
10 000 019
the smallest eight digit prime number.
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