The CAS Registry Mumber 87792-17-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,7,9 and 2 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 87792-17: (7*8)+(6*7)+(5*7)+(4*9)+(3*2)+(2*1)+(1*7)=184 184 % 10 = 4 So 87792-17-4 is a valid CAS Registry Number.