18744221 has 2 divisors, whose sum is σ = 18744222. Its totient is φ = 18744220.

The previous prime is 18744157. The next prime is 18744223. The reversal of 18744221 is 12244781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17131321 + 1612900 = 4139^2 + 1270^2 .

It is an emirp because it is prime and its reverse (12244781) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18744221 - 2⁶ = 18744157 is a prime.

Together with 18744223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18744223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9372110 + 9372111.

It is an arithmetic number, because the mean of its divisors is an integer number (9372111).

Almost surely, 2^18744221 is an apocalyptic number.

It is an amenable number.

18744221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18744221 is an equidigital number, since it uses as much as digits as its factorization.

18744221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3584, while the sum is 29.

The square root of 18744221 is about 4329.4596660553. The cubic root of 18744221 is about 265.6373456961.

The spelling of 18744221 in words is "eighteen million, seven hundred forty-four thousand, two hundred twenty-one".