The CAS Registry Mumber 26177-38-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,6,1,7 and 7 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 26177-38: (7*2)+(6*6)+(5*1)+(4*7)+(3*7)+(2*3)+(1*8)=118 118 % 10 = 8 So 26177-38-8 is a valid CAS Registry Number.