The CAS Registry Mumber 65708-57-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,7,0 and 8 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 65708-57: (7*6)+(6*5)+(5*7)+(4*0)+(3*8)+(2*5)+(1*7)=148 148 % 10 = 8 So 65708-57-8 is a valid CAS Registry Number.