161516561 has 4 divisors (see below), whose sum is σ = 162695652. Its totient is φ = 160337472.

The previous prime is 161516501. The next prime is 161516567. The reversal of 161516561 is 165615161.

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 32262400 + 129254161 = 5680^2 + 11369^2 .

It is a cyclic number.

It is not a de Polignac number, because 161516561 - 2⁶ = 161516497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161516567) 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, 589340 + ... + 589613.

It is an arithmetic number, because the mean of its divisors is an integer number (40673913).

Almost surely, 2^161516561 is an apocalyptic number.

It is an amenable number.

161516561 is a deficient number, since it is larger than the sum of its proper divisors (1179091).

161516561 is a wasteful number, since it uses less digits than its factorization.

161516561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1179090.

The product of its digits is 5400, while the sum is 32.

The square root of 161516561 is about 12708.9165942656. The cubic root of 161516561 is about 544.5933739906.

The spelling of 161516561 in words is "one hundred sixty-one million, five hundred sixteen thousand, five hundred sixty-one".