74

This number is a composite.

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The only double-digit number ab such that (ab)^a-(ba)^b is prime, i.e., 74^7-47^4 = 12151275393343 that is a prime. [Loungrides]

Submitted: 2012-06-14 03:57:30; Last Modified: 2020-07-13 20:03:24.