991090489 has 2 divisors, whose sum is σ = 991090490. Its totient is φ = 991090488.

The previous prime is 991090487. The next prime is 991090501. The reversal of 991090489 is 984090199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 911738025 + 79352464 = 30195^2 + 8908^2 .

It is a cyclic number.

It is not a de Polignac number, because 991090489 - 2¹ = 991090487 is a prime.

Together with 991090487, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (991090487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495545244 + 495545245.

It is an arithmetic number, because the mean of its divisors is an integer number (495545245).

Almost surely, 2^991090489 is an apocalyptic number.

It is an amenable number.

991090489 is a deficient number, since it is larger than the sum of its proper divisors (1).

991090489 is an equidigital number, since it uses as much as digits as its factorization.

991090489 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 209952, while the sum is 49.

The square root of 991090489 is about 31481.5896834960. The cubic root of 991090489 is about 997.0212991509.

The spelling of 991090489 in words is "nine hundred ninety-one million, ninety thousand, four hundred eighty-nine".