991909009 has 32 divisors (see below), whose sum is σ = 1272499200. Its totient is φ = 767946816.

The previous prime is 991908991. The next prime is 991909021. The reversal of 991909009 is 900909199.

It is not a de Polignac number, because 991909009 - 2⁷ = 991908881 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 991909009.

It is not an unprimeable number, because it can be changed into a prime (991909409) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 207207 + ... + 211939.

It is an arithmetic number, because the mean of its divisors is an integer number (39765600).

Almost surely, 2^991909009 is an apocalyptic number.

It is an amenable number.

991909009 is a deficient number, since it is larger than the sum of its proper divisors (280590191).

991909009 is a wasteful number, since it uses less digits than its factorization.

991909009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4814 (or 4800 counting only the distinct ones).

The product of its (nonzero) digits is 59049, while the sum is 46.

The square root of 991909009 is about 31494.5869793525. The cubic root of 991909009 is about 997.2956963341.

The spelling of 991909009 in words is "nine hundred ninety-one million, nine hundred nine thousand, nine".