The CAS Registry Mumber 79887-26-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,9,8,8 and 7 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 79887-26: (7*7)+(6*9)+(5*8)+(4*8)+(3*7)+(2*2)+(1*6)=206 206 % 10 = 6 So 79887-26-6 is a valid CAS Registry Number.