The CAS Registry Mumber 78857-65-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,8,5 and 7 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 78857-65: (7*7)+(6*8)+(5*8)+(4*5)+(3*7)+(2*6)+(1*5)=195 195 % 10 = 5 So 78857-65-5 is a valid CAS Registry Number.