The CAS Registry Mumber 2985-35-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,9,8 and 5 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 2985-35: (6*2)+(5*9)+(4*8)+(3*5)+(2*3)+(1*5)=115 115 % 10 = 5 So 2985-35-5 is a valid CAS Registry Number.