Wolfram Mathematica, 47 bytes
Tr[z=LetterNumber@Characters@#]~Mod~Tr[1^z]==0&
Takes input as string, e.g.:
Tr[z=LetterNumber@Characters@#]~Mod~Tr[1^z]==0&@"abcb"
True
Tr[z=LetterNumber@Characters@#]~Mod~Tr[1^z]==0&
Takes input as string, e.g.:
Tr[z=LetterNumber@Characters@#]~Mod~Tr[1^z]==0&@"abcb"
True