163981 has 2 divisors, whose sum is σ = 163982. Its totient is φ = 163980.

The previous prime is 163979. The next prime is 163987. The reversal of 163981 is 189361.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 152100 + 11881 = 390^2 + 109^2 .

It is an emirp because it is prime and its reverse (189361) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 163981 - 2¹ = 163979 is a prime.

It is a super-3 number, since 3×163981³ = 13228233316815423, which contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 163979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (163987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81990 + 81991.

It is an arithmetic number, because the mean of its divisors is an integer number (81991).

2¹⁶³⁹⁸¹ is an apocalyptic number.

It is an amenable number.

163981 is a deficient number, since it is larger than the sum of its proper divisors (1).

163981 is an equidigital number, since it uses as much as digits as its factorization.

163981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 28.

The square root of 163981 is about 404.9456753689. The cubic root of 163981 is about 54.7349228377.

The spelling of 163981 in words is "one hundred sixty-three thousand, nine hundred eighty-one".