1556561 has 2 divisors, whose sum is σ = 1556562. Its totient is φ = 1556560.

The previous prime is 1556551. The next prime is 1556563. The reversal of 1556561 is 1656551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1547536 + 9025 = 1244^2 + 95^2 .

It is a cyclic number.

It is not a de Polignac number, because 1556561 - 2¹⁴ = 1540177 is a prime.

Together with 1556563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1556563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 778280 + 778281.

It is an arithmetic number, because the mean of its divisors is an integer number (778281).

2^1556561 is an apocalyptic number.

It is an amenable number.

1556561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1556561 is an equidigital number, since it uses as much as digits as its factorization.

1556561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4500, while the sum is 29.

The square root of 1556561 is about 1247.6221383095. The cubic root of 1556561 is about 115.8925133935.

The spelling of 1556561 in words is "one million, five hundred fifty-six thousand, five hundred sixty-one".