The CAS Registry Mumber 85858-77-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,5,8,5 and 8 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 85858-77: (7*8)+(6*5)+(5*8)+(4*5)+(3*8)+(2*7)+(1*7)=191 191 % 10 = 1 So 85858-77-1 is a valid CAS Registry Number.