218981 has 12 divisors (see below), whose sum is σ = 263340. Its totient is φ = 181440.

The previous prime is 218971. The next prime is 218987. The reversal of 218981 is 189812.

It can be written as a sum of positive squares in 2 ways, for example, as 70756 + 148225 = 266^2 + 385^2 .

It is a de Polignac number, because none of the positive numbers 2^k-218981 is a prime.

It is a super-2 number, since 2×218981² = 95905356722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is an alternating number because its digits alternate between even and odd.

218981 is a modest number, since divided by 981 gives 218 as remainder.

It is a plaindrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1955 + ... + 2063.

It is an arithmetic number, because the mean of its divisors is an integer number (21945).

2²¹⁸⁹⁸¹ is an apocalyptic number.

It is an amenable number.

218981 is a deficient number, since it is larger than the sum of its proper divisors (44359).

218981 is a wasteful number, since it uses less digits than its factorization.

218981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164 (or 157 counting only the distinct ones).

The product of its digits is 1152, while the sum is 29.

The square root of 218981 is about 467.9540575740. The cubic root of 218981 is about 60.2747583950.

The spelling of 218981 in words is "two hundred eighteen thousand, nine hundred eighty-one".