1555565661 has 16 divisors (see below), whose sum is σ = 2481814720. Its totient is φ = 957270960.

The previous prime is 1555565629. The next prime is 1555565681. The reversal of 1555565661 is 1665655551.

It is not a de Polignac number, because 1555565661 - 2⁵ = 1555565629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1555565681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2215555 + ... + 2216256.

It is an arithmetic number, because the mean of its divisors is an integer number (155113420).

Almost surely, 2^1555565661 is an apocalyptic number.

It is an amenable number.

1555565661 is a deficient number, since it is larger than the sum of its proper divisors (926249059).

1555565661 is a wasteful number, since it uses less digits than its factorization.

1555565661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4431833 (or 4431827 counting only the distinct ones).

The product of its digits is 675000, while the sum is 45.

The square root of 1555565661 is about 39440.6599970132. The cubic root of 1555565661 is about 1158.6780573468.

The spelling of 1555565661 in words is "one billion, five hundred fifty-five million, five hundred sixty-five thousand, six hundred sixty-one".