561166156561 has 4 divisors (see below), whose sum is σ = 561243984624. Its totient is φ = 561088328500.

The previous prime is 561166156547. The next prime is 561166156583. The reversal of 561166156561 is 165651661165.

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.

It is a cyclic number.

It is not a de Polignac number, because 561166156561 - 2¹¹ = 561166154513 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (561166156531) 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, 38903215 + ... + 38917636.

It is an arithmetic number, because the mean of its divisors is an integer number (140310996156).

Almost surely, 2^561166156561 is an apocalyptic number.

It is an amenable number.

561166156561 is a deficient number, since it is larger than the sum of its proper divisors (77828063).

561166156561 is an equidigital number, since it uses as much as digits as its factorization.

561166156561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77828062.

The product of its digits is 972000, while the sum is 49.

The spelling of 561166156561 in words is "five hundred sixty-one billion, one hundred sixty-six million, one hundred fifty-six thousand, five hundred sixty-one".