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BaseRepresentation
bin111011100110101…
…100100111111111
32120200200021010000
4323212230213333
54021444444444
6243121245343
733531600615
oct7346544777
92520607100
10999999999
11473523889
1223aa93853
1312c23a19b
1496b4b6b5
155cbd1469
hex3b9ac9ff

999999999 has 20 divisors (see below), whose sum is σ = 1534205464. Its totient is φ = 648646704.

The previous prime is 999999937. The next prime is 1000000007.

999999999 is nontrivially palindromic in base 10.

It is a Cunningham number, because it is equal to 109-1.

It is a trimorphic number since its cube, 999999997000000002999999999, ends in 999999999.

It is not a de Polignac number, because 999999999 - 29 = 999999487 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (81).

It is a nude number because it is divisible by every one of its digits.

It is a Duffinian number.

999999999 is a modest number, since divided by 99999 gives 9999 as remainder.

999999999 is a nontrivial repdigit in base 10.

It is a plaindrome in base 10.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999999929) by changing a digit.

It is a Kaprekar number, because its square (999999998000000001) can be partitioned into two parts whose sum is 999999999.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 163837 + ... + 169830.

Almost surely, 2999999999 is an apocalyptic number.

999999999 is a deficient number, since it is larger than the sum of its proper divisors (534205465).

999999999 is a wasteful number, since it uses less digits than its factorization.

999999999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333716 (or 333707 counting only the distinct ones).

The product of its digits is 387420489, while the sum is 81.

The square root of 999999999 is about 31622.7765858724. The cubic root of 999999999 is about 999.9999996667. Note that the first 6 decimals are identical.

The spelling of 999999999 in words is "nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine".