1. Let r2,r3,…,r1000 denote the remainders when a positive odd integer N is divided by 2,3,…,1000, respectively. It is given that these remainders are pairwise distinct and one of them is 0.
2. Assume N∈S, where S is the set of integers satisfying the given conditions. Let p be the unique integer for which rp=0.
3. If p is composite, there exists a prime q<p which divides p, implying rq=0. This is a contradiction since the remainders are pairwise distinct. Therefore, p must be a prime number.
4. Since N is odd, r2=1. This implies p=2.
5. The fact that 0≤rk≤k−1 implies r3=2, r4=3, r5=4, and so on, up to rp−1=p−2. This gives us the sequence:
rk=k−1for2≤k≤p−1.
6. Assume p<500. Then 2p<1000. Since rp=0, p divides r2p, implying r2p=p because r2p<2p and r2p=rp=0.
7. This combined with the sequence rk=k−1 for 2≤k≤p−1 and the fact that rp+1∈{0,1,2,…,p} implies rp+1=p−1. However, rp+1 must be odd since p is an odd prime, leading to a contradiction. Therefore, p>500.
8. Next, assume 500<p<1000. For positive integers k≤p, define the odd positive integer Nk=p1000!k−1.
9. Let m be an integer such that 2≤m≤1000 and m=p. Clearly, m divides p1000!, hence:
Nk≡−1≡m−1(modm),
i.e., the remainder is m−1 when Nk is divided by m.
10. Assume a and b are integers such that 1≤a<b≤p and Na≡Nb(modp). This implies:
p1000!a−1≡p1000!b−1(modp)⟹p1000!(b−a)≡0(modp).
Since 1≤a<b≤p, 0<b−a<p, hence p∤b−a. Also, p∤p1000! because p>500 implies 1000<2p<p2, meaning p2∤1000!. Consequently, Na≡Nb(modp).
11. Therefore, N1,N2,…,Np are congruent to 0,1,2,…,p−1 modulo p in some order. Thus, there is one unique integer c∈{1,2,…,p} such that Nc≡0(modp).
12. Summarizing, Nc has 999 distinct remainders when divided by 2,3,…,1000 and one of them is zero. Hence, Nc∈S, leading to the conclusion:
The values of k for which it is possible that rk=0 are all primes between 500 and 1000.
The final answer is all primes between 500 and 1000.