The CAS Registry Mumber 870-57-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 8,7 and 0 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 870-57: (5*8)+(4*7)+(3*0)+(2*5)+(1*7)=85 85 % 10 = 5 So 870-57-5 is a valid CAS Registry Number.