2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/75639We propose a divisibility test for all integers which have 1, 3, 7 or 9 in their unit's place. In particular, then, the test applies for all prime divisors except 2 and 5.7 pages, Latex, no figuresGeneral Mathematicstext