1800209 has 2 divisors, whose sum is σ = 1800210. Its totient is φ = 1800208.

The previous prime is 1800199. The next prime is 1800221. The reversal of 1800209 is 9020081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1697809 + 102400 = 1303^2 + 320^2 .

It is a cyclic number.

It is not a de Polignac number, because 1800209 - 2¹⁶ = 1734673 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1800259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 900104 + 900105.

It is an arithmetic number, because the mean of its divisors is an integer number (900105).

2^1800209 is an apocalyptic number.

It is an amenable number.

1800209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1800209 is an equidigital number, since it uses as much as digits as its factorization.

1800209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 1800209 is about 1341.7186739403. The cubic root of 1800209 is about 121.6487478041.

The spelling of 1800209 in words is "one million, eight hundred thousand, two hundred nine".