The CAS Registry Mumber 183674-78-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,3,6,7 and 4 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 183674-78: (8*1)+(7*8)+(6*3)+(5*6)+(4*7)+(3*4)+(2*7)+(1*8)=174 174 % 10 = 4 So 183674-78-4 is a valid CAS Registry Number.