1643221 has 2 divisors, whose sum is σ = 1643222. Its totient is φ = 1643220.

The previous prime is 1643219. The next prime is 1643231. The reversal of 1643221 is 1223461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1512900 + 130321 = 1230^2 + 361^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643221 - 2¹ = 1643219 is a prime.

Together with 1643219, it forms a pair of twin primes.

It is a Chen prime.

It is a d-powerful number, because it can be written as 1 + 6⁶ + 4³ + 3¹³ + 2⁷ + 2¹¹ + 1 .

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1643231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821610 + 821611.

It is an arithmetic number, because the mean of its divisors is an integer number (821611).

2^1643221 is an apocalyptic number.

It is an amenable number.

1643221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643221 is an equidigital number, since it uses as much as digits as its factorization.

1643221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 19.

The square root of 1643221 is about 1281.8818198258. The cubic root of 1643221 is about 118.0045243884.

Adding to 1643221 its reverse (1223461), we get a palindrome (2866682).

The spelling of 1643221 in words is "one million, six hundred forty-three thousand, two hundred twenty-one".