The CAS Registry Mumber 145241-91-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,5,2,4 and 1 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 145241-91: (8*1)+(7*4)+(6*5)+(5*2)+(4*4)+(3*1)+(2*9)+(1*1)=114 114 % 10 = 4 So 145241-91-4 is a valid CAS Registry Number.