161881 has 2 divisors, whose sum is σ = 161882.
Its totient is φ = 161880.
The previous prime is 161879. The next prime is 161911. The reversal of 161881 is 188161.
161881 = 2842 + 2852.
It is a happy number.
161881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 81225 + 80656 = 285^2 + 284^2
It is a cyclic number.
It is not a de Polignac number, because 161881 - 21 = 161879 is a prime.
It is a super-2 number, since 2×1618812 = 52410916322, which contains 22 as substring.
Together with 161879, it forms a pair of twin primes.
161881 is a lucky number.
It is not a weakly prime, because it can be changed into another prime (161831) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80940 + 80941.
It is an arithmetic number, because the mean of its divisors is an integer number (80941).
2161881 is an apocalyptic number.
161881 is the 285-th centered square number.
It is an amenable number.
161881 is a deficient number, since it is larger than the sum of its proper divisors (1).
161881 is an equidigital number, since it uses as much as digits as its factorization.
161881 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 384, while the sum is 25.
The square root of 161881 is about 402.3443798539.
The cubic root of 161881 is about 54.5002665307.
The spelling of 161881 in words is "one hundred sixty-one thousand, eight hundred eighty-one".