The CAS Registry Mumber 127154-84-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,7,1,5 and 4 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 127154-84: (8*1)+(7*2)+(6*7)+(5*1)+(4*5)+(3*4)+(2*8)+(1*4)=121 121 % 10 = 1 So 127154-84-1 is a valid CAS Registry Number.