The CAS Registry Mumber 1301738-66-8 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,0,1,7,3 and 8 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 1301738-66: (9*1)+(8*3)+(7*0)+(6*1)+(5*7)+(4*3)+(3*8)+(2*6)+(1*6)=128 128 % 10 = 8 So 1301738-66-8 is a valid CAS Registry Number.