865605509 has 2 divisors, whose sum is σ = 865605510. Its totient is φ = 865605508.

The previous prime is 865605493. The next prime is 865605563. The reversal of 865605509 is 905506568.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 539261284 + 326344225 = 23222^2 + 18065^2 .

It is a cyclic number.

It is not a de Polignac number, because 865605509 - 2⁴ = 865605493 is a prime.

It is a super-2 number, since 2×865605509² = 1498545794422298162, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 865605509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (865605599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432802754 + 432802755.

It is an arithmetic number, because the mean of its divisors is an integer number (432802755).

Almost surely, 2^865605509 is an apocalyptic number.

It is an amenable number.

865605509 is a deficient number, since it is larger than the sum of its proper divisors (1).

865605509 is an equidigital number, since it uses as much as digits as its factorization.

865605509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324000, while the sum is 44.

The square root of 865605509 is about 29421.1745006891. The cubic root of 865605509 is about 953.0302167561.

The spelling of 865605509 in words is "eight hundred sixty-five million, six hundred five thousand, five hundred nine".