Power of Two
Double it 19 times and you're done.
A number of the form 2ᵏ, like 1, 1024 or 524288. An old friend of computing — a single 1 followed by zeros in binary.
Your record
Only 20 powers of two live in the range (2⁰ through 2¹⁹), a mere 0.002% — 2²⁰ = 1,048,576 overshoots by a single step. They are the most geometric family here: each new member is a straight doubling.
Programmers have muscle memory for these numbers: 1024 is a K, 65536 is 64K, 262144 hides in memory specs. Because computers run on binary, RAM sizes, buffers and hash-table capacities all naturally grow into powers of two.
Trivia: subtract 1 from a power of two and you may land a Mersenne prime — the range holds three: 8191 = 2¹³−1, 131071 = 2¹⁷−1 and 524287 = 2¹⁹−1. Nearly all known record primes are of this form, hunted down by the distributed project GIMPS.