18996221 has 2 divisors, whose sum is σ = 18996222. Its totient is φ = 18996220.

The previous prime is 18996209. The next prime is 18996223. The reversal of 18996221 is 12269981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18619225 + 376996 = 4315^2 + 614^2 .

It is an emirp because it is prime and its reverse (12269981) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18996221 is a prime.

Together with 18996223, 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 (18996223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9498110 + 9498111.

It is an arithmetic number, because the mean of its divisors is an integer number (9498111).

Almost surely, 2^18996221 is an apocalyptic number.

It is an amenable number.

18996221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18996221 is an equidigital number, since it uses as much as digits as its factorization.

18996221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 38.

The square root of 18996221 is about 4358.4654409551. The cubic root of 18996221 is about 266.8224726644.

The spelling of 18996221 in words is "eighteen million, nine hundred ninety-six thousand, two hundred twenty-one".