The CAS Registry Mumber 87935-13-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,9,3 and 5 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 87935-13: (7*8)+(6*7)+(5*9)+(4*3)+(3*5)+(2*1)+(1*3)=175 175 % 10 = 5 So 87935-13-5 is a valid CAS Registry Number.