491908009 has 2 divisors, whose sum is σ = 491908010. Its totient is φ = 491908008.

The previous prime is 491907991. The next prime is 491908069. The reversal of 491908009 is 900809194.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 381342784 + 110565225 = 19528^2 + 10515^2 .

It is a cyclic number.

It is not a de Polignac number, because 491908009 - 2⁹ = 491907497 is a prime.

It is not a weakly prime, because it can be changed into another prime (491908069) 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, 245954004 + 245954005.

It is an arithmetic number, because the mean of its divisors is an integer number (245954005).

Almost surely, 2^491908009 is an apocalyptic number.

It is an amenable number.

491908009 is a deficient number, since it is larger than the sum of its proper divisors (1).

491908009 is an equidigital number, since it uses as much as digits as its factorization.

491908009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 491908009 is about 22178.9992785969. Note that the first 3 decimals coincide. The cubic root of 491908009 is about 789.3954724649.

The spelling of 491908009 in words is "four hundred ninety-one million, nine hundred eight thousand, nine".