The CAS Registry Mumber 55658-96-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,6,5 and 8 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 55658-96: (7*5)+(6*5)+(5*6)+(4*5)+(3*8)+(2*9)+(1*6)=163 163 % 10 = 3 So 55658-96-3 is a valid CAS Registry Number.