Those Fascinating Numbers 341
1 684 126 080 (= 27 · 35 · 5 · 72 · 13 · 17)
the third solution of
σ(n)
n
=
19
4
(see the number 746 444 160).
1 716 728 832 (=
210
·
32
· 7 · 11 · 13 · 23 · 89)
the fifth solution of
σ(n)
n
=
15
4
(see the number 293 760).
1 767 263 190
the
19th
Catalan number (see the number 14).
1 870 585 220
the number of twin prime pairs
1012
(see the number 1 224).
1 879 906 755
the fifth number which is not the square of a prime number, but which can be
written as the sum of the squares of some of its prime factors: here 1 879 906 755 =
3 · 5 · 2897 · 43261 = 52 + 28972 + 432612 (see the number 870).
1 903 757 312
the 15th Euler number (see the number 272).
1 934 917 632
the smallest fifth power which can be written as the sum of five fifth powers:
1 934 917 632 =
725
=
195
+
435
+
465
+
475
+
675
(Lander and Parkin, 1967).
1 977 225 901 (=
75
· 117 643)
the fourth 6-hyperperfect number (see the number 301).
2 012 783 315
the smallest number n which allows the sum
i≤n
1
i
to exceed 22 (see the number
83).
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