The CAS Registry Mumber 75616-26-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,6,1 and 6 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 75616-26: (7*7)+(6*5)+(5*6)+(4*1)+(3*6)+(2*2)+(1*6)=141 141 % 10 = 1 So 75616-26-1 is a valid CAS Registry Number.