18943921 has 2 divisors, whose sum is σ = 18943922. Its totient is φ = 18943920.

The previous prime is 18943913. The next prime is 18943937. The reversal of 18943921 is 12934981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11458225 + 7485696 = 3385^2 + 2736^2 .

It is a cyclic number.

It is not a de Polignac number, because 18943921 - 2³ = 18943913 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18943901) 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, 9471960 + 9471961.

It is an arithmetic number, because the mean of its divisors is an integer number (9471961).

Almost surely, 2^18943921 is an apocalyptic number.

It is an amenable number.

18943921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18943921 is an equidigital number, since it uses as much as digits as its factorization.

18943921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 37.

The square root of 18943921 is about 4352.4614874804. The cubic root of 18943921 is about 266.5773775716.

The spelling of 18943921 in words is "eighteen million, nine hundred forty-three thousand, nine hundred twenty-one".