The CAS Registry Mumber 84257-76-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,2,5 and 7 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 84257-76: (7*8)+(6*4)+(5*2)+(4*5)+(3*7)+(2*7)+(1*6)=151 151 % 10 = 1 So 84257-76-1 is a valid CAS Registry Number.