161505115106581 has 4 divisors (see below), whose sum is σ = 165444264255564. Its totient is φ = 157565965957600.

The previous prime is 161505115106497. The next prime is 161505115106639. The reversal of 161505115106581 is 185601511505161.

161505115106581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3801525062500 + 157703590044081 = 1949750^2 + 12558009^2 .

It is a cyclic number.

It is not a de Polignac number, because 161505115106581 - 2⁷ = 161505115106453 is a prime.

It is a super-2 number, since 2×161505115106581² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161505115106981) 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, 1969574574430 + ... + 1969574574511.

It is an arithmetic number, because the mean of its divisors is an integer number (41361066063891).

Almost surely, 2^{161505115106581} is an apocalyptic number.

It is an amenable number.

161505115106581 is a deficient number, since it is larger than the sum of its proper divisors (3939149148983).

161505115106581 is an equidigital number, since it uses as much as digits as its factorization.

161505115106581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3939149148982.

The product of its (nonzero) digits is 180000, while the sum is 46.

The spelling of 161505115106581 in words is "one hundred sixty-one trillion, five hundred five billion, one hundred fifteen million, one hundred six thousand, five hundred eighty-one".