The CAS Registry Mumber 61950-54-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,1,9,5 and 0 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 61950-54: (7*6)+(6*1)+(5*9)+(4*5)+(3*0)+(2*5)+(1*4)=127 127 % 10 = 7 So 61950-54-7 is a valid CAS Registry Number.