The CAS Registry Mumber 115523-77-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,5,5,2 and 3 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 115523-77: (8*1)+(7*1)+(6*5)+(5*5)+(4*2)+(3*3)+(2*7)+(1*7)=108 108 % 10 = 8 So 115523-77-8 is a valid CAS Registry Number.