# 13

This number is a prime.

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13333333333333/13 is prime. The numerator has thirteen 3's following 1. [Poo Sung]

The 13th Mersenne prime is 2^{521} - 1 and the 13th Lucas number is 521. [Poo Sung]

Girolamo Cardano (1501-1576) divided cubic equations into 13 types (excluding x^3 = c and equations reducible to quadratics) in his work *Ars Magna*, which was the first Latin treatise devoted solely to algebra. [Poo Sung]

13 is the smallest prime having only one 1. [Poo Sung]

At most 13 baseball players can be in play: 9 fielders, 3 runners, and 1 batter. [Poo Sung]

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