The CAS Registry Mumber 53458-85-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,3,4,5 and 8 respectively; the second part has 2 digits, 8 and 5 respectively. Calculate Digit Verification of CAS Registry Number 53458-85: (7*5)+(6*3)+(5*4)+(4*5)+(3*8)+(2*8)+(1*5)=138 138 % 10 = 8 So 53458-85-8 is a valid CAS Registry Number.