1998221 has 2 divisors, whose sum is σ = 1998222. Its totient is φ = 1998220.

The previous prime is 1998209. The next prime is 1998223. The reversal of 1998221 is 1228991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1020100 + 978121 = 1010^2 + 989^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1998221 is a prime.

Together with 1998223, 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 (1998223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999110 + 999111.

It is an arithmetic number, because the mean of its divisors is an integer number (999111).

2^1998221 is an apocalyptic number.

It is an amenable number.

1998221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1998221 is an equidigital number, since it uses as much as digits as its factorization.

1998221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 32.

The square root of 1998221 is about 1413.5844509615. The cubic root of 1998221 is about 125.9547372486.

The spelling of 1998221 in words is "one million, nine hundred ninety-eight thousand, two hundred twenty-one".