The CAS Registry Mumber 82155-58-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,1,5 and 5 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 82155-58: (7*8)+(6*2)+(5*1)+(4*5)+(3*5)+(2*5)+(1*8)=126 126 % 10 = 6 So 82155-58-6 is a valid CAS Registry Number.