1816556561 has 2 divisors, whose sum is σ = 1816556562. Its totient is φ = 1816556560.

The previous prime is 1816556531. The next prime is 1816556587. The reversal of 1816556561 is 1656556181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1811353600 + 5202961 = 42560^2 + 2281^2 .

It is a cyclic number.

It is not a de Polignac number, because 1816556561 - 2²⁶ = 1749447697 is a prime.

It is not a weakly prime, because it can be changed into another prime (1816556501) 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, 908278280 + 908278281.

It is an arithmetic number, because the mean of its divisors is an integer number (908278281).

Almost surely, 2^1816556561 is an apocalyptic number.

It is an amenable number.

1816556561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1816556561 is an equidigital number, since it uses as much as digits as its factorization.

1816556561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216000, while the sum is 44.

The square root of 1816556561 is about 42621.0811805613. The cubic root of 1816556561 is about 1220.1586645296.

The spelling of 1816556561 in words is "one billion, eight hundred sixteen million, five hundred fifty-six thousand, five hundred sixty-one".