161605 has 4 divisors (see below), whose sum is σ = 193932. Its totient is φ = 129280.

The previous prime is 161599. The next prime is 161611. The reversal of 161605 is 506161.

It is a Cunningham number, because it is equal to 402²+1.

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

It is an interprime number because it is at equal distance from previous prime (161599) and next prime (161611).

It can be written as a sum of positive squares in 2 ways, for example, as 58564 + 103041 = 242^2 + 321^2 .

It is not a de Polignac number, because 161605 - 2⁵ = 161573 is a prime.

It is a super-2 number, since 2×161605² = 52232352050, which contains 22 as substring.

It is a Duffinian number.

161605 is a lucky 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, 16156 + ... + 16165.

It is an arithmetic number, because the mean of its divisors is an integer number (48483).

2¹⁶¹⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

161605 is a deficient number, since it is larger than the sum of its proper divisors (32327).

161605 is an equidigital number, since it uses as much as digits as its factorization.

161605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32326.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 161605 is about 402.0012437792. The cubic root of 161605 is about 54.4692753904.

Adding to 161605 its reverse (506161), we get a palindrome (667766).

The spelling of 161605 in words is "one hundred sixty-one thousand, six hundred five".