1820809 has 2 divisors, whose sum is σ = 1820810. Its totient is φ = 1820808.

The previous prime is 1820783. The next prime is 1820813. The reversal of 1820809 is 9080281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1814409 + 6400 = 1347^2 + 80^2 .

It is a cyclic number.

It is not a de Polignac number, because 1820809 - 2¹⁵ = 1788041 is a prime.

It is a plaindrome in base 14.

It is not a weakly prime, because it can be changed into another prime (1820869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910404 + 910405.

It is an arithmetic number, because the mean of its divisors is an integer number (910405).

2^1820809 is an apocalyptic number.

It is an amenable number.

1820809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1820809 is an equidigital number, since it uses as much as digits as its factorization.

1820809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 1820809 is about 1349.3735583596. The cubic root of 1820809 is about 122.1110026188. Note that the first 3 decimals are identical.

The spelling of 1820809 in words is "one million, eight hundred twenty thousand, eight hundred nine".