18038821 has 2 divisors, whose sum is σ = 18038822. Its totient is φ = 18038820.

The previous prime is 18038803. The next prime is 18038843. The reversal of 18038821 is 12883081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17724100 + 314721 = 4210^2 + 561^2 .

It is a cyclic number.

It is not a de Polignac number, because 18038821 - 2⁵ = 18038789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18038851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9019410 + 9019411.

It is an arithmetic number, because the mean of its divisors is an integer number (9019411).

Almost surely, 2^18038821 is an apocalyptic number.

It is an amenable number.

18038821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18038821 is an equidigital number, since it uses as much as digits as its factorization.

18038821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3072, while the sum is 31.

The square root of 18038821 is about 4247.2133216969. The cubic root of 18038821 is about 262.2624111758.

The spelling of 18038821 in words is "eighteen million, thirty-eight thousand, eight hundred twenty-one".