18966821 has 2 divisors, whose sum is σ = 18966822. Its totient is φ = 18966820.

The previous prime is 18966817. The next prime is 18966859. The reversal of 18966821 is 12866981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9541921 + 9424900 = 3089^2 + 3070^2 .

It is a cyclic number.

It is not a de Polignac number, because 18966821 - 2² = 18966817 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18966121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9483410 + 9483411.

It is an arithmetic number, because the mean of its divisors is an integer number (9483411).

Almost surely, 2^18966821 is an apocalyptic number.

It is an amenable number.

18966821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18966821 is an equidigital number, since it uses as much as digits as its factorization.

18966821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 41.

The square root of 18966821 is about 4355.0913882489. The cubic root of 18966821 is about 266.6847499890.

The spelling of 18966821 in words is "eighteen million, nine hundred sixty-six thousand, eight hundred twenty-one".