The CAS Registry Mumber 99676-74-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,6,7 and 6 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 99676-74: (7*9)+(6*9)+(5*6)+(4*7)+(3*6)+(2*7)+(1*4)=211 211 % 10 = 1 So 99676-74-1 is a valid CAS Registry Number.