In 1936, Krull asked if the integral closure of a primary ideal is still primary. Fifty years later, Huneke partially answered this question by giving a primary polynomial ideal whose integral closure is not primary in a regular local ring of characteristic p = 2. In this paper, we give counterexamples to Krull's question in terms of polynomial rings with any characteristics. It is amazing that the Jacobian ideal of the polynomial f = x 6 + y 6 + x 4 zt + z 3 given by Briançon and Speder in 1975 also provides a counterexample to Krull's question. This example was used by Briançon and Speder to show that the pair (V1 \ V2, V2) satisfies Whitney's conditions but fails Zariski equisingularity conditions, where V1 is the hypersurface defined by f = 0 and V2 is the singular locus of V1. Most surprisingly, we show that the pair (V1 \ V2, V2) does not satisfy Whitney's conditions: there are three points (0, 0, 0, − 3 27/4ω) (ω 3 = 1) on V2 such that Whitney's conditions fail! Moreover, we also show that Whitney stratification of this hypersurface is different from the stratification of isosingular sets given by Hauenstein and Wampler, which is related to Thom-Boardman singularity.