The CAS Registry Mumber 99548-17-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,5,4 and 8 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 99548-17: (7*9)+(6*9)+(5*5)+(4*4)+(3*8)+(2*1)+(1*7)=191 191 % 10 = 1 So 99548-17-1 is a valid CAS Registry Number.