61666610505561 has 10 divisors (see below), whose sum is σ = 92119257668922. Its totient is φ = 41111073670320.

The previous prime is 61666610505517. The next prime is 61666610505581. The reversal of 61666610505561 is 16550501666616.

61666610505561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 31791159873225 + 29875450632336 = 5638365^2 + 5465844^2 .

It is not a de Polignac number, because 61666610505561 - 2²⁷ = 61666476287833 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 61666610505498 and 61666610505507.

It is not an unprimeable number, because it can be changed into a prime (61666610505581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 380658089460 + ... + 380658089621.

Almost surely, 2^{61666610505561} is an apocalyptic number.

It is an amenable number.

61666610505561 is a deficient number, since it is larger than the sum of its proper divisors (30452647163361).

61666610505561 is an equidigital number, since it uses as much as digits as its factorization.

61666610505561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 761316179093 (or 761316179084 counting only the distinct ones).

The product of its (nonzero) digits is 5832000, while the sum is 54.

The spelling of 61666610505561 in words is "sixty-one trillion, six hundred sixty-six billion, six hundred ten million, five hundred five thousand, five hundred sixty-one".