18206821 has 2 divisors, whose sum is σ = 18206822. Its totient is φ = 18206820.

The previous prime is 18206789. The next prime is 18206831. The reversal of 18206821 is 12860281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12852225 + 5354596 = 3585^2 + 2314^2 .

It is a cyclic number.

It is not a de Polignac number, because 18206821 - 2⁵ = 18206789 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18206821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18206831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9103410 + 9103411.

It is an arithmetic number, because the mean of its divisors is an integer number (9103411).

Almost surely, 2^18206821 is an apocalyptic number.

It is an amenable number.

18206821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18206821 is an equidigital number, since it uses as much as digits as its factorization.

18206821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 18206821 is about 4266.9451601819. The cubic root of 18206821 is about 263.0740682052.

The spelling of 18206821 in words is "eighteen million, two hundred six thousand, eight hundred twenty-one".