The CAS Registry Mumber 71690-59-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,1,6,9 and 0 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 71690-59: (7*7)+(6*1)+(5*6)+(4*9)+(3*0)+(2*5)+(1*9)=140 140 % 10 = 0 So 71690-59-0 is a valid CAS Registry Number.