The CAS Registry Mumber 2954-90-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,9,5 and 4 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 2954-90: (6*2)+(5*9)+(4*5)+(3*4)+(2*9)+(1*0)=107 107 % 10 = 7 So 2954-90-7 is a valid CAS Registry Number.