1998209 has 2 divisors, whose sum is σ = 1998210. Its totient is φ = 1998208.

The previous prime is 1998181. The next prime is 1998221. The reversal of 1998209 is 9028991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1890625 + 107584 = 1375^2 + 328^2 .

It is an emirp because it is prime and its reverse (9028991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1998209 - 2²⁰ = 949633 is a prime.

It is not a weakly prime, because it can be changed into another prime (1998289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999104 + 999105.

It is an arithmetic number, because the mean of its divisors is an integer number (999105).

2^1998209 is an apocalyptic number.

It is an amenable number.

1998209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1998209 is an equidigital number, since it uses as much as digits as its factorization.

1998209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 38.

The square root of 1998209 is about 1413.5802064262. The cubic root of 1998209 is about 125.9544851144.

The spelling of 1998209 in words is "one million, nine hundred ninety-eight thousand, two hundred nine".