18528721 has 2 divisors, whose sum is σ = 18528722. Its totient is φ = 18528720.

The previous prime is 18528707. The next prime is 18528751. The reversal of 18528721 is 12782581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16810000 + 1718721 = 4100^2 + 1311^2 .

It is a cyclic number.

It is not a de Polignac number, because 18528721 - 2¹⁷ = 18397649 is a prime.

It is the 4305-th Hogben number.

It is not a weakly prime, because it can be changed into another prime (18528701) by changing a digit.

It is a nontrivial repunit in base 4304.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9264360 + 9264361.

It is an arithmetic number, because the mean of its divisors is an integer number (9264361).

Almost surely, 2^18528721 is an apocalyptic number.

It is an amenable number.

18528721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18528721 is an equidigital number, since it uses as much as digits as its factorization.

18528721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8960, while the sum is 34.

The square root of 18528721 is about 4304.5000871181. The cubic root of 18528721 is about 264.6154193643.

The spelling of 18528721 in words is "eighteen million, five hundred twenty-eight thousand, seven hundred twenty-one".