18000221 has 2 divisors, whose sum is σ = 18000222. Its totient is φ = 18000220.

The previous prime is 18000217. The next prime is 18000259. The reversal of 18000221 is 12200081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12888100 + 5112121 = 3590^2 + 2261^2 .

It is a cyclic number.

It is not a de Polignac number, because 18000221 - 2² = 18000217 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 18000196 and 18000205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18000721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9000110 + 9000111.

It is an arithmetic number, because the mean of its divisors is an integer number (9000111).

Almost surely, 2^18000221 is an apocalyptic number.

It is an amenable number.

18000221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18000221 is an equidigital number, since it uses as much as digits as its factorization.

18000221 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 18000221 is about 4242.6667321391. Note that the first 3 decimals coincide. The cubic root of 18000221 is about 262.0752119792.

The spelling of 18000221 in words is "eighteen million, two hundred twenty-one", and thus it is an aban number.