161611605 has 40 divisors (see below), whose sum is σ = 306758232. Its totient is φ = 81119232.

The previous prime is 161611601. The next prime is 161611607. The reversal of 161611605 is 506116161.

It can be written as a sum of positive squares in 4 ways, for example, as 84768849 + 76842756 = 9207^2 + 8766^2 .

It is not a de Polignac number, because 161611605 - 2² = 161611601 is a prime.

It is a super-2 number, since 2×161611605² = 52236621741352050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161611601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 4852 + ... + 18621.

Almost surely, 2^161611605 is an apocalyptic number.

161611605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161611605 is a deficient number, since it is larger than the sum of its proper divisors (145146627).

161611605 is a wasteful number, since it uses less digits than its factorization.

161611605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23507 (or 23498 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 161611605 is about 12712.6553087858. The cubic root of 161611605 is about 544.7001745624.

Adding to 161611605 its reverse (506116161), we get a palindrome (667727766).

It can be divided in two parts, 16161 and 1605, that added together give a triangular number (17766 = T₁₈₈).

The spelling of 161611605 in words is "one hundred sixty-one million, six hundred eleven thousand, six hundred five".