1281809 has 2 divisors, whose sum is σ = 1281810. Its totient is φ = 1281808.

The previous prime is 1281803. The next prime is 1281821. The reversal of 1281809 is 9081821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1203409 + 78400 = 1097^2 + 280^2 .

It is a cyclic number.

It is not a de Polignac number, because 1281809 - 2¹⁶ = 1216273 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1281803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 640904 + 640905.

It is an arithmetic number, because the mean of its divisors is an integer number (640905).

2^1281809 is an apocalyptic number.

It is an amenable number.

1281809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1281809 is an equidigital number, since it uses as much as digits as its factorization.

1281809 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 29.

The square root of 1281809 is about 1132.1700402325. The cubic root of 1281809 is about 108.6278303933.

The spelling of 1281809 in words is "one million, two hundred eighty-one thousand, eight hundred nine".