The CAS Registry Mumber 136776-26-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,6,7,7 and 6 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 136776-26: (8*1)+(7*3)+(6*6)+(5*7)+(4*7)+(3*6)+(2*2)+(1*6)=156 156 % 10 = 6 So 136776-26-6 is a valid CAS Registry Number.