The CAS Registry Mumber 121825-88-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,1,8,2 and 5 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 121825-88: (8*1)+(7*2)+(6*1)+(5*8)+(4*2)+(3*5)+(2*8)+(1*8)=115 115 % 10 = 5 So 121825-88-5 is a valid CAS Registry Number.