The CAS Registry Mumber 84770-90-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,7,7 and 0 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 84770-90: (7*8)+(6*4)+(5*7)+(4*7)+(3*0)+(2*9)+(1*0)=161 161 % 10 = 1 So 84770-90-1 is a valid CAS Registry Number.