The CAS Registry Mumber 25529-35-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,5,5,2 and 9 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 25529-35: (7*2)+(6*5)+(5*5)+(4*2)+(3*9)+(2*3)+(1*5)=115 115 % 10 = 5 So 25529-35-5 is a valid CAS Registry Number.