Ten prime digits with a set product

How many 1010-digit numbers have all digits prime (each digit in {2,3,5,7}\{2, 3, 5, 7\}) and a digit-product equal to exactly 100000100000?

Show hints (2)+
  1. 100000=2555100000=2^5\cdot5^5. Digits are prime - 33s and 77s can't appear, so every digit is 22 or 55.
  2. Need exactly five 22s and five 55s in 1010 slots: (105)\binom{10}{5}.

Answer

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252

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Asked at: Jane Street, Two Sigma

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