161605321 has 4 divisors (see below), whose sum is σ = 164654532. Its totient is φ = 158556112.

The previous prime is 161605319. The next prime is 161605331. The reversal of 161605321 is 123506161.

161605321 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, and also an emirpimes, since its reverse is a distinct semiprime: 123506161 = 859 ⋅143779.

It can be written as a sum of positive squares in 2 ways, for example, as 53860921 + 107744400 = 7339^2 + 10380^2 .

It is a cyclic number.

It is not a de Polignac number, because 161605321 - 2¹ = 161605319 is a prime.

It is a super-2 number, since 2×161605321² = 52232559551026082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161605331) 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, 1524526 + ... + 1524631.

It is an arithmetic number, because the mean of its divisors is an integer number (41163633).

Almost surely, 2^161605321 is an apocalyptic number.

It is an amenable number.

161605321 is a deficient number, since it is larger than the sum of its proper divisors (3049211).

161605321 is an equidigital number, since it uses as much as digits as its factorization.

161605321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3049210.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 161605321 is about 12712.4081510940. The cubic root of 161605321 is about 544.6931145490.

The spelling of 161605321 in words is "one hundred sixty-one million, six hundred five thousand, three hundred twenty-one".