The CAS Registry Mumber 35557-67-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,5,5,5 and 7 respectively; the second part has 2 digits, 6 and 7 respectively. Calculate Digit Verification of CAS Registry Number 35557-67: (7*3)+(6*5)+(5*5)+(4*5)+(3*7)+(2*6)+(1*7)=136 136 % 10 = 6 So 35557-67-6 is a valid CAS Registry Number.