991912209 has 16 divisors (see below), whose sum is σ = 1416087360. Its totient is φ = 615380480.

The previous prime is 991912171. The next prime is 991912241. The reversal of 991912209 is 902219199.

991912209 = T₃₀₂ + T₃₀₃ + ... + T₁₈₁₄.

991912209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 991912209 - 2²³ = 983523601 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991912249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 104727 + ... + 113804.

It is an arithmetic number, because the mean of its divisors is an integer number (88505460).

Almost surely, 2^991912209 is an apocalyptic number.

It is an amenable number.

991912209 is a deficient number, since it is larger than the sum of its proper divisors (424175151).

991912209 is a wasteful number, since it uses less digits than its factorization.

991912209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218640.

The product of its (nonzero) digits is 26244, while the sum is 42.

The square root of 991912209 is about 31494.6377816923. The cubic root of 991912209 is about 997.2967687923.

The spelling of 991912209 in words is "nine hundred ninety-one million, nine hundred twelve thousand, two hundred nine".