161891 has 8 divisors (see below), whose sum is σ = 174960. Its totient is φ = 149248.

The previous prime is 161881. The next prime is 161911. The reversal of 161891 is 198161.

161891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161891 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 161891.

It is not an unprimeable number, because it can be changed into a prime (161831) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1460 + ... + 1566.

It is an arithmetic number, because the mean of its divisors is an integer number (21870).

2¹⁶¹⁸⁹¹ is an apocalyptic number.

161891 is a deficient number, since it is larger than the sum of its proper divisors (13069).

161891 is a wasteful number, since it uses less digits than its factorization.

161891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213.

The product of its digits is 432, while the sum is 26.

The square root of 161891 is about 402.3568068270. The cubic root of 161891 is about 54.5013887366.

The spelling of 161891 in words is "one hundred sixty-one thousand, eight hundred ninety-one".