The CAS Registry Mumber 84855-58-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,8,5 and 5 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 84855-58: (7*8)+(6*4)+(5*8)+(4*5)+(3*5)+(2*5)+(1*8)=173 173 % 10 = 3 So 84855-58-3 is a valid CAS Registry Number.