161890565 has 4 divisors (see below), whose sum is σ = 194268684. Its totient is φ = 129512448.

The previous prime is 161890549. The next prime is 161890601. The reversal of 161890565 is 565098161.

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 47100769 + 114789796 = 6863^2 + 10714^2 .

It is a cyclic number.

It is not a de Polignac number, because 161890565 - 2⁴ = 161890549 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16189052 + ... + 16189061.

It is an arithmetic number, because the mean of its divisors is an integer number (48567171).

Almost surely, 2^161890565 is an apocalyptic number.

It is an amenable number.

161890565 is a deficient number, since it is larger than the sum of its proper divisors (32378119).

161890565 is an equidigital number, since it uses as much as digits as its factorization.

161890565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32378118.

The product of its (nonzero) digits is 64800, while the sum is 41.

The square root of 161890565 is about 12723.6223222791. The cubic root of 161890565 is about 545.0133992161.

The spelling of 161890565 in words is "one hundred sixty-one million, eight hundred ninety thousand, five hundred sixty-five".