145

This number is a composite.

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145 is the smallest number that occurs as the digit sum of both (2p−1)ᵖ⁻¹ + (p−1)ᵖ and (2p−1)ᵖ⁻¹ − (p−1)ᵖ for some prime p. For p = 19, these are 37¹⁸ ± 18¹⁹, and both have a digit sum of 145. Curiously, 145 is also the digit sum of both 37¹⁹ and 37¹⁹ + 18¹⁹. [Ahmed]