# 504

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## Number

$504$ (five hundred and four) is:

$2^3 \times 3^2 \times 7$

The $1$st positive integer which can be expressed as the product of $2$ two-digit numbers in $2$ ways such that the factors in one of those pairs is the reversal of each of the factors in the other:
$504 = 12 \times 42 = 21 \times 24$

The $24$th positive integer after $64$, $96$, $128$, $144$, $\ldots$, $384$, $400$, $416$, $432$, $448$, $480$, $504$ with $6$ or more prime factors:
$504 = 2 \times 2 \times 2 \times 3 \times 3 \times 7$

The $37$th highly abundant number after $1$, $2$, $3$, $4$, $6$, $8$, $10$, $\ldots$, $120$, $144$, $168$, $180$, $210$, $216$, $240$, $288$, $300$, $336$, $360$, $420$, $480$:
$\map \sigma {504} = 1560$