1156665561 has 16 divisors (see below), whose sum is σ = 1616385024. Its totient is φ = 734324624.

The previous prime is 1156665553. The next prime is 1156665571. The reversal of 1156665561 is 1655666511.

It is a cyclic number.

It is not a de Polignac number, because 1156665561 - 2³ = 1156665553 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1156665511) 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, 21261 + ... + 52586.

It is an arithmetic number, because the mean of its divisors is an integer number (101024064).

Almost surely, 2^1156665561 is an apocalyptic number.

It is an amenable number.

1156665561 is a deficient number, since it is larger than the sum of its proper divisors (459719463).

1156665561 is a wasteful number, since it uses less digits than its factorization.

1156665561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74100.

The product of its digits is 162000, while the sum is 42.

The square root of 1156665561 is about 34009.7862533712. The cubic root of 1156665561 is about 1049.7098400052.

The spelling of 1156665561 in words is "one billion, one hundred fifty-six million, six hundred sixty-five thousand, five hundred sixty-one".