OlympiadSuperchallengeOlympiad Number Theory ShareOlympiad Number Theory · Superchallenge problemHow many ODD primes p≤100p \le 100p≤100 have −1-1−1 as a quadratic residue, i.e. admit a solution to x2≡−1(modp)x^2 \equiv -1 \pmod px2≡−1(modp)?Check Show answer Walk through it step by step Practice more like this Review this concept