161391617 has 4 divisors (see below), whose sum is σ = 162569796. Its totient is φ = 160213440.

The previous prime is 161391589. The next prime is 161391619. The reversal of 161391617 is 716193161.

It is a Cunningham number, because it is equal to 12704²+1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 716193161 = 397 ⋅1804013.

It can be written as a sum of positive squares in 2 ways, for example, as 94789696 + 66601921 = 9736^2 + 8161^2 .

It is a cyclic number.

It is not a de Polignac number, because 161391617 - 2⁸ = 161391361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161391619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 588884 + ... + 589157.

It is an arithmetic number, because the mean of its divisors is an integer number (40642449).

Almost surely, 2^161391617 is an apocalyptic number.

It is an amenable number.

161391617 is a deficient number, since it is larger than the sum of its proper divisors (1178179).

161391617 is a wasteful number, since it uses less digits than its factorization.

161391617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1178178.

The product of its digits is 6804, while the sum is 35.

The square root of 161391617 is about 12704.0000393577. Note that the first 4 decimals coincide. The cubic root of 161391617 is about 544.4529111445.

The spelling of 161391617 in words is "one hundred sixty-one million, three hundred ninety-one thousand, six hundred seventeen".