Those Fascinating Numbers 251
246 683
the number of Carmichael numbers
1016
(see the number 646).
247 141
the smallest prime number equally distant, by a distance of 42, from the pre-
ceding and following prime numbers: p21805 = 247 099, p21806 = 247 141 and
p21807 = 247 183.
248 397
the smallest number n which allows the sum
i≤n
1
i
to exceed 13 (see the number
83).
248 832 (=
125)
the smallest fifth power which can be written as the sum of six fifth powers:
248 832 =
125
=
45
+
55
+
65
+
75
+
95
+
115
(Martin, 1887).
253 472 (= 2 · 5 ·
892)
the 1 000th powerful number (see the number 3 136).
254 540
the smallest number n such that ω(n) = ω(n + 1) = 5; in fact, 254 540 =
22
· 5 · 11 · 13 · 89 and 254 541 = 3 · 7 · 17 · 23 · 31 (see the number 230).
255 803
the smallest prime number equally distant, by a distance of 36, from the pre-
ceding and following prime numbers: p22506 = 255 767, p22507 = 255 803 and
p22508 = 255 839.
261 120
the sixth number n divisible by a square 1 and such that γ(n + 1) γ(n) = 1
(see the number 48).
262 419
the tenth number n 1 such that n · 2n + 1 is prime (see the number 141).
Previous Page Next Page