The CAS Registry Mumber 2790-12-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,7,9 and 0 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 2790-12: (6*2)+(5*7)+(4*9)+(3*0)+(2*1)+(1*2)=87 87 % 10 = 7 So 2790-12-7 is a valid CAS Registry Number.