The word MATHEMATICIAN has 13 letters, with the letter M appearing twice, the letter A appearing twice, the letter T appearing twice, and the letter I appearing three times. The number of ways to arrange these letters is given by the formula for permutations of multisets:

\( \frac{n!}{k_1! \cdot k_2! \cdot ... \cdot k_m!} \)

where \(n\) is the total number of elements in the multiset and \(k_1, k_2, ..., k_m\) are the multiplicities of the distinct elements.

Substituting the values for this problem, we get:

\( \frac{13!}{2! \cdot 2! \cdot 2! \cdot 3!} = \frac{6227020800}{2 \cdot 2 \cdot 2 \cdot 6} = 129729600 \)