1805561 has 2 divisors, whose sum is σ = 1805562. Its totient is φ = 1805560.

The previous prime is 1805549. The next prime is 1805579. The reversal of 1805561 is 1655081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1336336 + 469225 = 1156^2 + 685^2 .

It is a cyclic number.

It is not a de Polignac number, because 1805561 - 2⁶ = 1805497 is a prime.

It is a Chen prime.

It is equal to p₁₃₅₄₄₉ and since 1805561 and 135449 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1805561.

It is not a weakly prime, because it can be changed into another prime (1805501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 902780 + 902781.

It is an arithmetic number, because the mean of its divisors is an integer number (902781).

2^1805561 is an apocalyptic number.

It is an amenable number.

1805561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1805561 is an equidigital number, since it uses as much as digits as its factorization.

1805561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1200, while the sum is 26.

The square root of 1805561 is about 1343.7116506156. The cubic root of 1805561 is about 121.7691819611.

The spelling of 1805561 in words is "one million, eight hundred five thousand, five hundred sixty-one".