2620

Number
$2620$ (two thousand, six hundred and twenty) is:
 * $2^2 \times 5 \times 131$


 * The smaller of the $3$rd amicable pair, with $2924$:
 * $\sigma \left({2620}\right) = \sigma \left({2924}\right) = 5544 = 2620 + 2924$