1806561 has 12 divisors (see below), whose sum is σ = 2626260. Its totient is φ = 1196640.

The previous prime is 1806557. The next prime is 1806569. The reversal of 1806561 is 1656081.

1806561 is a `hidden beast` number, since 1 + 8 + 0 + 656 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 24336 + 1782225 = 156^2 + 1335^2 .

It is not a de Polignac number, because 1806561 - 2² = 1806557 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1806569) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1075 + ... + 2183.

It is an arithmetic number, because the mean of its divisors is an integer number (218855).

2^1806561 is an apocalyptic number.

It is an amenable number.

1806561 is a deficient number, since it is larger than the sum of its proper divisors (819699).

1806561 is a wasteful number, since it uses less digits than its factorization.

1806561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1296 (or 1293 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 1806561 is about 1344.0837027507. The cubic root of 1806561 is about 121.7916582087.

The spelling of 1806561 in words is "one million, eight hundred six thousand, five hundred sixty-one".