1205809 has 4 divisors (see below), whose sum is σ = 1315440. Its totient is φ = 1096180.

The previous prime is 1205779. The next prime is 1205819. The reversal of 1205809 is 9085021.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1205809 - 2⁷ = 1205681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1205819) 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, 54799 + ... + 54820.

It is an arithmetic number, because the mean of its divisors is an integer number (328860).

2^1205809 is an apocalyptic number.

It is an amenable number.

1205809 is a deficient number, since it is larger than the sum of its proper divisors (109631).

1205809 is a wasteful number, since it uses less digits than its factorization.

1205809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109630.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 1205809 is about 1098.0933475803. The cubic root of 1205809 is about 106.4370527387.

It can be divided in two parts, 120 and 5809, that added together give a square (5929 = 77²).

The spelling of 1205809 in words is "one million, two hundred five thousand, eight hundred nine".