Teaser 2659: Two by two

From The Sunday Times, 8th September 2013 [link] [link]

I have given each letter of the alphabet a different value from 0 to 25, so some letters represent a single digit and some represent two digits.

Therefore, for example, a three-letter word could represent a number of three, four, five or six digits. With my values it turns out that:

TWO × TWO = FOUR

Another “obvious” fact that I can tell you is that every digit occurring in TWO is a prime!

What is the number FOUR?

Interestingly, one of the earliest published alphametic puzzles was:

TWO × TWO = THREE

(using more usual alphametic rules), which appeared almost 100 years ago in the July 1924 issue of Strand Magazine.

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