Those Fascinating Numbers 255
342 225
the seventh of the existing eight primitive non deficient numbers (see the num-
ber 945).
343 027 (= 37 · 73 · 127)
the smallest square-free composite number n such that p|n =⇒ p + 8|n + 8.
344 160
the 13th number n such that σ(n) and σ2(n) have the same prime factors,
namely the primes 2, 3, 5, 7 and 13 (see the number 180).
346 065 (= 3 · 5 · 23 071)
the smallest number n which allows the sum
m≤n
ω(m)=3
1
m
to exceed 3 (see the
number 1 953).
353 792
the
11th
Euler number (see the number 272).
357 966
the only six digit number which can be written as the addition and/or subtrac-
tion of the factorials of its digits in two distinct ways; indeed,
357 966 = 3! + 5! 7! + 9! + 6! 6! = 3! + 5! 7! + 9! 6! + 6!;
observe also that 357 941 = 3!+5! 7!+9! 4! 1!, 361 469 = 3! 6! 1!+4!
6!+9!, 367 209 = 3! 6!+7!+2!+0!+9! and 398 173 = 3!+9!+8!+1! 7!+3!.
361 275
the 11th number n 1 such that n · 2n + 1 is prime (see the number 141).
obtains

1234567898765432112345678987654321 =
32
· 37 ·

11133366688900000111333666889,

123456789876543211234567898765432112345678987654321
=
32
· 37 ·

1113336668890000011133366688900000111333666889,
and so on.
Previous Page Next Page