The CAS Registry Mumber 142981-41-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,2,9,8 and 1 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 142981-41: (8*1)+(7*4)+(6*2)+(5*9)+(4*8)+(3*1)+(2*4)+(1*1)=137 137 % 10 = 7 So 142981-41-7 is a valid CAS Registry Number.