The CAS Registry Mumber 35541-68-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,5,5,4 and 1 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 35541-68: (7*3)+(6*5)+(5*5)+(4*4)+(3*1)+(2*6)+(1*8)=115 115 % 10 = 5 So 35541-68-5 is a valid CAS Registry Number.