1166555661561 has 16 divisors (see below), whose sum is σ = 1730877237120. Its totient is φ = 776512792080.

The previous prime is 1166555661527. The next prime is 1166555661569. The reversal of 1166555661561 is 1651665556611.

1166555661561 is a `hidden beast` number, since 1 + 1 + 6 + 6 + 5 + 5 + 566 + 15 + 61 = 666.

It is not a de Polignac number, because 1166555661561 - 2⁷ = 1166555661433 is a prime.

It is a super-2 number, since 2×1166555661561² (a number of 25 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1166555661498 and 1166555661507.

It is not an unprimeable number, because it can be changed into a prime (1166555661569) 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, 33064885 + ... + 33100146.

It is an arithmetic number, because the mean of its divisors is an integer number (108179827320).

Almost surely, 2^{1166555661561} is an apocalyptic number.

It is an amenable number.

1166555661561 is a deficient number, since it is larger than the sum of its proper divisors (564321575559).

1166555661561 is an equidigital number, since it uses as much as digits as its factorization.

1166555661561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66165693 (or 66165687 counting only the distinct ones).

The product of its digits is 4860000, while the sum is 54.

The spelling of 1166555661561 in words is "one trillion, one hundred sixty-six billion, five hundred fifty-five million, six hundred sixty-one thousand, five hundred sixty-one".