218381 has 2 divisors, whose sum is σ = 218382.
Its totient is φ = 218380.
The previous prime is 218371. The next prime is 218389. The reversal of 218381 is 183812.
218381 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 217156 + 1225 = 466^2 + 35^2
It is a cyclic number.
It is not a de Polignac number, because 218381 - 214 = 201997 is a prime.
It is a super-2 number, since 2×2183812 = 95380522322, which contains 22 as substring.
It is a Chen prime.
It is an alternating number because its digits alternate between even and odd.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (218389) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109190 + 109191.
It is an arithmetic number, because the mean of its divisors is an integer number (109191).
2218381 is an apocalyptic number.
It is an amenable number.
218381 is a deficient number, since it is larger than the sum of its proper divisors (1).
218381 is an equidigital number, since it uses as much as digits as its factorization.
218381 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 384, while the sum is 23.
The square root of 218381 is about 467.3125292564.
The cubic root of 218381 is about 60.2196578223.
The spelling of 218381 in words is "two hundred eighteen thousand, three hundred eighty-one".