6638221 has 2 divisors, whose sum is σ = 6638222. Its totient is φ = 6638220.

The previous prime is 6638179. The next prime is 6638227. The reversal of 6638221 is 1228366.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4708900 + 1929321 = 2170^2 + 1389^2 .

It is a cyclic number.

It is not a de Polignac number, because 6638221 - 2¹¹ = 6636173 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 6638221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6638227) 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, 3319110 + 3319111.

It is an arithmetic number, because the mean of its divisors is an integer number (3319111).

Almost surely, 2^6638221 is an apocalyptic number.

It is an amenable number.

6638221 is a deficient number, since it is larger than the sum of its proper divisors (1).

6638221 is an equidigital number, since it uses as much as digits as its factorization.

6638221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 28.

The square root of 6638221 is about 2576.4745292745. The cubic root of 6638221 is about 187.9391401767.

It can be divided in two parts, 6638 and 221, that added together give a cube (6859 = 19³).

The spelling of 6638221 in words is "six million, six hundred thirty-eight thousand, two hundred twenty-one".