19999999

19999999 is the eight-digit natural number in base-10 notation, equal to 19,999,999. It is the value just below twenty million and is the successor of 19,999,998 and the predecessor of 20,000,000. In decimal form it is 1 followed by seven 9s, which makes it a common example in discussions of numbers near round figures.

As a mathematical object, 19,999,999 is odd, and its digit sum is 64, which implies it is not divisible by 3 or 9. It is not even and does not end in 0 or 5, so it is not divisible by 2 or 5. Determining whether it is prime requires a primality test; it is not among the small, commonly cited primes, and its factorization would require computation for verification.

In other bases the representation differs and does not exhibit the same simple pattern as in decimal. Conversions are routine and depend on standard numeral-system algorithms.

In practical use, numbers near 20 million appear in software testing as upper bounds for 8-digit identifiers, in performance benchmarks, and in examples illustrating decimal rounding, digit patterns, or arithmetic with large integers. The number is also often referenced as an example of a decimal number that is close to a round figure.

See also: 19999998, 20000000.