# 61

This number is a prime.

Just showing those entries submitted by 'Firoozbakht': (Click here to show all)

61 is the smallest number m and only two-digit number *m*
such that the reversal of concatenation of the first *m*
natural numbers is prime. [Firoozbakht]

61!*16! - 1 is prime with prime sum of digits. [Firoozbakht]

61 is the 7th prime of the form 3k+1 and 61 = (77+777)/(7+7). Note that seven 7's are used. [Firoozbakht]

(There is one curio for this number that has not yet been approved by an editor.)

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