18221389 has 2 divisors, whose sum is σ = 18221390. Its totient is φ = 18221388.

The previous prime is 18221341. The next prime is 18221393. The reversal of 18221389 is 98312281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15920100 + 2301289 = 3990^2 + 1517^2 .

It is a cyclic number.

It is not a de Polignac number, because 18221389 - 2⁹ = 18220877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18221339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9110694 + 9110695.

It is an arithmetic number, because the mean of its divisors is an integer number (9110695).

Almost surely, 2^18221389 is an apocalyptic number.

It is an amenable number.

18221389 is a deficient number, since it is larger than the sum of its proper divisors (1).

18221389 is an equidigital number, since it uses as much as digits as its factorization.

18221389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 34.

The square root of 18221389 is about 4268.6518949195. The cubic root of 18221389 is about 263.1442148334.

The spelling of 18221389 in words is "eighteen million, two hundred twenty-one thousand, three hundred eighty-nine".