1291040809 has 4 divisors (see below), whose sum is σ = 1366984404. Its totient is φ = 1215097216.

The previous prime is 1291040797. The next prime is 1291040827. The reversal of 1291040809 is 9080401921.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 736579600 + 554461209 = 27140^2 + 23547^2 .

It is a cyclic number.

It is not a de Polignac number, because 1291040809 - 2¹¹ = 1291038761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1291040869) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37971772 + ... + 37971805.

It is an arithmetic number, because the mean of its divisors is an integer number (341746101).

Almost surely, 2^1291040809 is an apocalyptic number.

It is an amenable number.

1291040809 is a deficient number, since it is larger than the sum of its proper divisors (75943595).

1291040809 is an equidigital number, since it uses as much as digits as its factorization.

1291040809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75943594.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 1291040809 is about 35931.0563301443. The cubic root of 1291040809 is about 1088.8799225514.

The spelling of 1291040809 in words is "one billion, two hundred ninety-one million, forty thousand, eight hundred nine".