Let N>1 and let ΦN (X, Y), Y be the modular polynomial which vanishes precisely at pairs of j-invariants of elliptic curves linked by a cyclic isogeny of degree N. In this note we study the divisibility of the coefficients ΦN (X+J, Y+J) for certain algebraic numbers J, in particular J=0 and J=1728. It turns out that these coefficients are highly divisible by small primes at which J is supersingular.
Florian Breuer (Mon,) studied this question.
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