A number of linear congruences modulo r are proved for the number of p
artitions that are p-cores where p is prime, 5 less-than-or-equal-to p
less-than-or-equal-to 23, and r is any prime divisor of 1/2(p - 1). A
nalogous results are derived for the number of irreducible p-modular r
epresentations of the symmetric group S(n). The congruences are proved
using the theory of modular forms.