1261565009 has 2 divisors, whose sum is σ = 1261565010. Its totient is φ = 1261565008.

The previous prime is 1261564979. The next prime is 1261565017. The reversal of 1261565009 is 9005651621.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 941262400 + 320302609 = 30680^2 + 17897^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1261565009 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1261565009.

It is not a weakly prime, because it can be changed into another prime (1261565029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630782504 + 630782505.

It is an arithmetic number, because the mean of its divisors is an integer number (630782505).

Almost surely, 2^1261565009 is an apocalyptic number.

It is an amenable number.

1261565009 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261565009 is an equidigital number, since it uses as much as digits as its factorization.

1261565009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16200, while the sum is 35.

The square root of 1261565009 is about 35518.5164245355. The cubic root of 1261565009 is about 1080.5292927421.

The spelling of 1261565009 in words is "one billion, two hundred sixty-one million, five hundred sixty-five thousand, nine".