18668821 has 2 divisors, whose sum is σ = 18668822. Its totient is φ = 18668820.

The previous prime is 18668809. The next prime is 18668833. The reversal of 18668821 is 12886681.

It is a balanced prime because it is at equal distance from previous prime (18668809) and next prime (18668833).

It can be written as a sum of positive squares in only one way, i.e., 18584721 + 84100 = 4311^2 + 290^2 .

It is a cyclic number.

It is not a de Polignac number, because 18668821 - 2⁷ = 18668693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18668861) by changing a digit.

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, 9334410 + 9334411.

It is an arithmetic number, because the mean of its divisors is an integer number (9334411).

Almost surely, 2^18668821 is an apocalyptic number.

It is an amenable number.

18668821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18668821 is an equidigital number, since it uses as much as digits as its factorization.

18668821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36864, while the sum is 40.

The square root of 18668821 is about 4320.7431073833. The cubic root of 18668821 is about 265.2806851524.

The spelling of 18668821 in words is "eighteen million, six hundred sixty-eight thousand, eight hundred twenty-one".