The CAS Registry Mumber 53857-91-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,3,8,5 and 7 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 53857-91: (7*5)+(6*3)+(5*8)+(4*5)+(3*7)+(2*9)+(1*1)=153 153 % 10 = 3 So 53857-91-3 is a valid CAS Registry Number.