The CAS Registry Mumber 126525-17-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,6,5,2 and 5 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 126525-17: (8*1)+(7*2)+(6*6)+(5*5)+(4*2)+(3*5)+(2*1)+(1*7)=115 115 % 10 = 5 So 126525-17-5 is a valid CAS Registry Number.