Yes, EIGENVALUE is a Scrabble word!

Letter values in Scrabble US: E 1, I 1, G 2, E 1, N 1, V 4, A 1, L 1, U 1, E 1.

Is it a valid word?

EIGENVALUE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(mathematics) any number such that a given square matrix minus that number times the identity matrix has a zero determinant

Also: eigenvalue of a matrix, eigenvalue of a square matrix, characteristic root of a square matrix.