161573561 has 4 divisors (see below), whose sum is σ = 165940452. Its totient is φ = 157206672.

The previous prime is 161573539. The next prime is 161573563. The reversal of 161573561 is 165375161.

161573561 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 56715961 + 104857600 = 7531^2 + 10240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161573561 is a prime.

It is a super-2 number, since 2×161573561² = 52212031228441442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161573563) 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, 2183390 + ... + 2183463.

It is an arithmetic number, because the mean of its divisors is an integer number (41485113).

Almost surely, 2^161573561 is an apocalyptic number.

It is an amenable number.

161573561 is a deficient number, since it is larger than the sum of its proper divisors (4366891).

161573561 is an equidigital number, since it uses as much as digits as its factorization.

161573561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4366890.

The product of its digits is 18900, while the sum is 35.

The square root of 161573561 is about 12711.1589164796. The cubic root of 161573561 is about 544.6574296953.

The spelling of 161573561 in words is "one hundred sixty-one million, five hundred seventy-three thousand, five hundred sixty-one".