18255821 has 2 divisors, whose sum is σ = 18255822. Its totient is φ = 18255820.

The previous prime is 18255817. The next prime is 18255829. The reversal of 18255821 is 12855281.

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., 12075625 + 6180196 = 3475^2 + 2486^2 .

It is a cyclic number.

It is not a de Polignac number, because 18255821 - 2² = 18255817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18255829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9127910 + 9127911.

It is an arithmetic number, because the mean of its divisors is an integer number (9127911).

Almost surely, 2^18255821 is an apocalyptic number.

It is an amenable number.

18255821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18255821 is an equidigital number, since it uses as much as digits as its factorization.

18255821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6400, while the sum is 32.

The square root of 18255821 is about 4272.6831148589. The cubic root of 18255821 is about 263.3098604654.

The spelling of 18255821 in words is "eighteen million, two hundred fifty-five thousand, eight hundred twenty-one".