The CAS Registry Mumber 84787-66-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,7,8 and 7 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 84787-66: (7*8)+(6*4)+(5*7)+(4*8)+(3*7)+(2*6)+(1*6)=186 186 % 10 = 6 So 84787-66-6 is a valid CAS Registry Number.