576
This number is a composite.
576 = sigma(5*7*6). Note that 576 is the first multi-digit
number with this property. [Firoozbakht]
A square equal to (2 + 3 + 5 + 7 + 11)2 - (22 + 32 + 52 + 72 + 112). It's the only such case for all primes < 2,000,000,000. [Trotter and
De Geest]
576 is the largest known square that divides the concatenation of its prime factors, where the order of its prime factors can be arranged freely, i.e. 576 = 2 * 2 * 2 * 2 * 3 * 2 * 3 * 2, and 576 divides 22223232. [Rivera]
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