1256809 has 2 divisors, whose sum is σ = 1256810. Its totient is φ = 1256808.

The previous prime is 1256797. The next prime is 1256813. The reversal of 1256809 is 9086521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 896809 + 360000 = 947^2 + 600^2 .

It is an emirp because it is prime and its reverse (9086521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1256809 - 2⁵ = 1256777 is a prime.

1256809 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (1256819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628404 + 628405.

It is an arithmetic number, because the mean of its divisors is an integer number (628405).

2^1256809 is an apocalyptic number.

It is an amenable number.

1256809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256809 is an equidigital number, since it uses as much as digits as its factorization.

1256809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 1256809 is about 1121.0749305912. The cubic root of 1256809 is about 107.9169743701.

Adding to 1256809 its product of nonzero digits (4320), we get a square (1261129 = 1123²).

The spelling of 1256809 in words is "one million, two hundred fifty-six thousand, eight hundred nine".