161989 has 4 divisors (see below), whose sum is σ = 169056. Its totient is φ = 154924.

The previous prime is 161983. The next prime is 161999. The reversal of 161989 is 989161.

161989 = T₁₀₇ + T₁₀₈ + ... + T₁₂₉.

161989 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 161989 - 2⁵ = 161957 is a prime.

It is a super-2 number, since 2×161989² = 52480872242, which contains 22 as substring.

It is a Duffinian number.

161989 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3499 + ... + 3544.

It is an arithmetic number, because the mean of its divisors is an integer number (42264).

2¹⁶¹⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

161989 is a deficient number, since it is larger than the sum of its proper divisors (7067).

161989 is an equidigital number, since it uses as much as digits as its factorization.

161989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7066.

The product of its digits is 3888, while the sum is 34.

The square root of 161989 is about 402.4785708581. The cubic root of 161989 is about 54.5123839097.

The spelling of 161989 in words is "one hundred sixty-one thousand, nine hundred eighty-nine".