999981009 has 6 divisors (see below), whose sum is σ = 1444417026. Its totient is φ = 666654000.

The previous prime is 999980923. The next prime is 999981011. The reversal of 999981009 is 900189999.

It can be written as a sum of positive squares in only one way, i.e., 977937984 + 22043025 = 31272^2 + 4695^2 .

It is not a de Polignac number, because 999981009 - 2¹⁶ = 999915473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (999981049) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55554492 + ... + 55554509.

It is an arithmetic number, because the mean of its divisors is an integer number (240736171).

Almost surely, 2^999981009 is an apocalyptic number.

It is an amenable number.

999981009 is a deficient number, since it is larger than the sum of its proper divisors (444436017).

999981009 is a wasteful number, since it uses less digits than its factorization.

999981009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111109007 (or 111109004 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 54.

The square root of 999981009 is about 31622.4763261829. The cubic root of 999981009 is about 999.9936696266.

The spelling of 999981009 in words is "nine hundred ninety-nine million, nine hundred eighty-one thousand, nine".