A positive integer with exactly two different divisors greater than 1 must be
(A)a prime
(B)an even integer
(C)a multiple of 3
(D)the square of a prime
(E)the square of an odd integer
from:錢永強GRE難題, section3 第19題
mega \$m[1]:
The "reflection" of a positive integer is obtained by reversing its digits. For example, 321 is the reflection of 123.
The difference between a five-digit integer and its reflection must be divisible by which of the following?
(A)2 (B)4 (C)5 (D)6 (E)9
Ans:E
from:PP2
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