261308809 has 2 divisors, whose sum is σ = 261308810. Its totient is φ = 261308808.

The previous prime is 261308791. The next prime is 261308833. The reversal of 261308809 is 908803162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 257698809 + 3610000 = 16053^2 + 1900^2 .

It is a cyclic number.

It is not a de Polignac number, because 261308809 - 2¹¹ = 261306761 is a prime.

It is not a weakly prime, because it can be changed into another prime (261308849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130654404 + 130654405.

It is an arithmetic number, because the mean of its divisors is an integer number (130654405).

Almost surely, 2^261308809 is an apocalyptic number.

It is an amenable number.

261308809 is a deficient number, since it is larger than the sum of its proper divisors (1).

261308809 is an equidigital number, since it uses as much as digits as its factorization.

261308809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 261308809 is about 16165.0489946675. The cubic root of 261308809 is about 639.3195967233.

The spelling of 261308809 in words is "two hundred sixty-one million, three hundred eight thousand, eight hundred nine".