182 Jean-Marie De Koninck
9 567
the only solution “SEND” to the first known cryptogram
SEND + MORE = MONEY,
9 567 + 1 085 = 10 652
(see the number 1 085).
9 587
the smallest prime number that is preceded by 35 consecutive composite num-
bers; indeed, there are no prime numbers between 9 551 and 9 587.
9 592
the number of prime numbers 100 000.
9 623
the smallest prime factor of the Mersenne number
2283
1, whose complete
factorization is given by
2283
1 = 9623 · 68492481833 · P71.
9 689
the exponent of the
21rst
Mersenne prime
29 689
1 (Gillies, 1963).
9 800
the fourth powerful number n such that n + 1 is also powerful (see the number
288): here 9 800 =
23
·
52
·
72
and 9 801 =
34
·
112;
the fifth solution w + s of the aligned houses problem (see the number 35).
9 801
the sixth number n such that the binomial coefficient
(
n
2
)
is a perfect square:
here
(9
801
2
)
= 6
9302
(see the number 289).
9 865
the number of digits in the decimal expansion of the Fermat number
2215
+ 1.
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