Those Fascinating Numbers 281
1 999 999
the largest number n = [d1, d2, . . . , dr] such that d1!+ d2!+ . . . + dr ! n, where
d1, d2, . . . , dr stand for the digits of n: here 1! + 9! + 9! + 9! + 9! + 9! + 9! =
2 177 281 1 999 999.
2 013 216
the tenth number n such that φ(n) + σ(n) = 3n (see the number 312).
2 016 496
the smallest number which can be written as the sum of three distinct cubes
in seven distinct ways:
2 016 496 =
63
+
723
+
1183
=
103
+
663
+
1203
=
193
+
213
+
1263
=
473
+
973
+
1003
=
543
+
603
+
1183
=
663
+
903
+
1003
=
833
+
853
+
943
(see the number 1 009).
2 025 797
the eighth self contained number (see the number 293).
2 066 115
the smallest seven digit Sastry number (see the number 6 099).
2 118 656
the
11th
dihedral perfect number (see the number 130).
2 124 679
the second (and largest known) Wolstenholme prime (see the number 16 843).
2 142 720
the third solution of
σ(n)
n
=
11
3
(see the number 35 640).
2 178 540 (= 22 · 32 · 5 · 72 · 13 · 19)
the third 4-perfect number (see the number 30 240).
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