161561056011561 has 16 divisors (see below), whose sum is σ = 241586625816000. Its totient is φ = 106700759731584.

The previous prime is 161561056011557. The next prime is 161561056011577. The reversal of 161561056011561 is 165110650165161.

161561056011561 is a `hidden beast` number, since 1 + 6 + 1 + 5 + 6 + 10 + 5 + 60 + 11 + 561 = 666.

It is not a de Polignac number, because 161561056011561 - 2² = 161561056011557 is a prime.

It is a super-2 number, since 2×161561056011561² (a number of 29 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161561056031561) 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 15 ways as a sum of consecutive naturals, for example, 27961412136 + ... + 27961417913.

It is an arithmetic number, because the mean of its divisors is an integer number (15099164113500).

Almost surely, 2^{161561056011561} is an apocalyptic number.

It is an amenable number.

161561056011561 is a deficient number, since it is larger than the sum of its proper divisors (80025569804439).

161561056011561 is a wasteful number, since it uses less digits than its factorization.

161561056011561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55922830165 (or 55922830159 counting only the distinct ones).

The product of its (nonzero) digits is 162000, while the sum is 45.

The spelling of 161561056011561 in words is "one hundred sixty-one trillion, five hundred sixty-one billion, fifty-six million, eleven thousand, five hundred sixty-one".