161643665 has 16 divisors (see below), whose sum is σ = 198979968. Its totient is φ = 125991936.

The previous prime is 161643661. The next prime is 161643683. The reversal of 161643665 is 566346161.

It is a cyclic number.

It is not a de Polignac number, because 161643665 - 2² = 161643661 is a prime.

It is a super-2 number, since 2×161643665² = 52257348869264450, which contains 22 as substring.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161643661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 123404 + ... + 124706.

It is an arithmetic number, because the mean of its divisors is an integer number (12436248).

Almost surely, 2^161643665 is an apocalyptic number.

It is an amenable number.

161643665 is a deficient number, since it is larger than the sum of its proper divisors (37336303).

161643665 is a wasteful number, since it uses less digits than its factorization.

161643665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1928.

The product of its digits is 77760, while the sum is 38.

The square root of 161643665 is about 12713.9161944697. The cubic root of 161643665 is about 544.7361908145.

The spelling of 161643665 in words is "one hundred sixty-one million, six hundred forty-three thousand, six hundred sixty-five".