The CAS Registry Mumber 77856-30-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,8,5 and 6 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 77856-30: (7*7)+(6*7)+(5*8)+(4*5)+(3*6)+(2*3)+(1*0)=175 175 % 10 = 5 So 77856-30-5 is a valid CAS Registry Number.