218021 has 2 divisors, whose sum is σ = 218022. Its totient is φ = 218020.

The previous prime is 218003. The next prime is 218047. The reversal of 218021 is 120812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 172225 + 45796 = 415^2 + 214^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 217987 and 218005.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 218021.

It is not a weakly prime, because it can be changed into another prime (218081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109010 + 109011.

It is an arithmetic number, because the mean of its divisors is an integer number (109011).

2²¹⁸⁰²¹ is an apocalyptic number.

It is an amenable number.

218021 is a deficient number, since it is larger than the sum of its proper divisors (1).

218021 is an equidigital number, since it uses as much as digits as its factorization.

218021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 218021 is about 466.9271891848. The cubic root of 218021 is about 60.1865490196.

Adding to 218021 its reverse (120812), we get a palindrome (338833).

The spelling of 218021 in words is "two hundred eighteen thousand, twenty-one".