1566655561 has 3 divisors (see below), whose sum is σ = 1566695143. Its totient is φ = 1566615980.

The previous prime is 1566655549. The next prime is 1566655579. The reversal of 1566655561 is 1655566651.

The square root of 1566655561 is 39581.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1063999161 + 502656400 = 32619^2 + 22420^2 .

It is not a de Polignac number, because 1566655561 - 2²⁹ = 1029784649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1566655501) 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 in 2 ways as a sum of consecutive naturals, for example, 19791 + ... + 59371.

Almost surely, 2^1566655561 is an apocalyptic number.

1566655561 is the 39581-st square number.

1566655561 is the 19791-st centered octagonal number.

It is an amenable number.

1566655561 is a deficient number, since it is larger than the sum of its proper divisors (39582).

1566655561 is an frugal number, since it uses more digits than its factorization.

1566655561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79162 (or 39581 counting only the distinct ones).

The product of its digits is 810000, while the sum is 46.

The cubic root of 1566655561 is about 1161.4250127341.

The spelling of 1566655561 in words is "one billion, five hundred sixty-six million, six hundred fifty-five thousand, five hundred sixty-one".