157

Number
$157$ (one hundred and fifty-seven) is:


 * The $37$th prime number


 * The $12$th emirp after $13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149$


 * The $9$th of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 8^2 + 29 = 157$


 * The $1$st positive integer $n$ for which $\phi \left({2 n + 1}\right) < \phi \left({2 n}\right)$:
 * $\phi \left({2 \times 157 + 1}\right) = 144, \phi \left({2 \times 157}\right) = 156$

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