Solution:
The answer is (A). Observe that N=102024+1 and that a divisor of it of the required type is written as 10n+1 for some 1<n<2024. Let us therefore assume that 10n+1 divides N and write
N=102024+1=(10n+1)(102024−n)+r1,
from which r1=−(102024−n−1). Since N is divisible by 10n+1, r1 is also divisible by 10n+1. Repeating the same procedure, we obtain
−r1=102024−n−1=(10n+1)(102024−2n)+r2,
from which r2=−(102024−2n+1) is divisible by 10n+1 (essentially we are performing a sort of long division, in which however we allow the remainder to be negative).
Iterating this reasoning we obtain that 102024−2kn+1 is a multiple of 10n+1 for every k such that 2024−2kn is positive, and similarly 102024−(2k+1)n−1 must be a multiple of 10n+1 for every k such that 2024−(2k+1)n is positive. In particular, by choosing k appropriately we can make 2024−2kn or 2024−(2k+1)n positive and less than or equal to n (this essentially amounts to carrying out the division with remainder between 2024 and n): we then obtain that 10n+1 divides a number of the form 10a±1 with 1≤a≤n. If a were strictly less than n, clearly 10a±1 would be less than 10n+1, and hence could not be a multiple of it. It must therefore happen that a=n and that the sign is positive, which occurs only if n=2024−2kn, that is 2024=(2k+1)n. Thus n must be a proper divisor of 2024 with the property that 2024/n is odd, that is n=23d, where d is a proper divisor of 2024/23=253=11⋅23. There are therefore 3 possibilities: n=23,n=23⋅11,n=23⋅23.