6611611561 has 4 divisors (see below), whose sum is σ = 6611776000. Its totient is φ = 6611447124.

The previous prime is 6611611529. The next prime is 6611611607. The reversal of 6611611561 is 1651161166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1651161166 = 2 ⋅825580583.

It is a cyclic number.

It is not a de Polignac number, because 6611611561 - 2⁵ = 6611611529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6611611861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22840 + ... + 117238.

It is an arithmetic number, because the mean of its divisors is an integer number (1652944000).

Almost surely, 2^6611611561 is an apocalyptic number.

It is an amenable number.

6611611561 is a deficient number, since it is larger than the sum of its proper divisors (164439).

6611611561 is an equidigital number, since it uses as much as digits as its factorization.

6611611561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164438.

The product of its digits is 6480, while the sum is 34.

The square root of 6611611561 is about 81311.8168595439. The cubic root of 6611611561 is about 1876.8768464621.

It can be divided in two parts, 66116 and 11561, that added together give a palindrome (77677).

The spelling of 6611611561 in words is "six billion, six hundred eleven million, six hundred eleven thousand, five hundred sixty-one".