The CAS Registry Mumber 87705-26-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,7,0 and 5 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 87705-26: (7*8)+(6*7)+(5*7)+(4*0)+(3*5)+(2*2)+(1*6)=158 158 % 10 = 8 So 87705-26-8 is a valid CAS Registry Number.