The CAS Registry Mumber 7716-07-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,1 and 6 respectively; the second part has 2 digits, 0 and 7 respectively. Calculate Digit Verification of CAS Registry Number 7716-07: (6*7)+(5*7)+(4*1)+(3*6)+(2*0)+(1*7)=106 106 % 10 = 6 So 7716-07-6 is a valid CAS Registry Number.