18788921 has 2 divisors, whose sum is σ = 18788922. Its totient is φ = 18788920.

The previous prime is 18788911. The next prime is 18788941. The reversal of 18788921 is 12988781.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11971600 + 6817321 = 3460^2 + 2611^2 .

It is a cyclic number.

It is not a de Polignac number, because 18788921 - 2⁶ = 18788857 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18788911) 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, 9394460 + 9394461.

It is an arithmetic number, because the mean of its divisors is an integer number (9394461).

Almost surely, 2^18788921 is an apocalyptic number.

It is an amenable number.

18788921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18788921 is an equidigital number, since it uses as much as digits as its factorization.

18788921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64512, while the sum is 44.

The square root of 18788921 is about 4334.6188990498. The cubic root of 18788921 is about 265.8483362918.

The spelling of 18788921 in words is "eighteen million, seven hundred eighty-eight thousand, nine hundred twenty-one".