18528221 has 2 divisors, whose sum is σ = 18528222. Its totient is φ = 18528220.

The previous prime is 18528197. The next prime is 18528281. The reversal of 18528221 is 12282581.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18156121 + 372100 = 4261^2 + 610^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18528221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18528281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9264110 + 9264111.

It is an arithmetic number, because the mean of its divisors is an integer number (9264111).

Almost surely, 2^18528221 is an apocalyptic number.

It is an amenable number.

18528221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18528221 is an equidigital number, since it uses as much as digits as its factorization.

18528221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2560, while the sum is 29.

The square root of 18528221 is about 4304.4420079727. The cubic root of 18528221 is about 264.6130391155.

The spelling of 18528221 in words is "eighteen million, five hundred twenty-eight thousand, two hundred twenty-one".