The CAS Registry Mumber 82961-54-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,9,6 and 1 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 82961-54: (7*8)+(6*2)+(5*9)+(4*6)+(3*1)+(2*5)+(1*4)=154 154 % 10 = 4 So 82961-54-4 is a valid CAS Registry Number.