6438721 has 2 divisors, whose sum is σ = 6438722. Its totient is φ = 6438720.

The previous prime is 6438697. The next prime is 6438749. The reversal of 6438721 is 1278346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5948721 + 490000 = 2439^2 + 700^2 .

It is a cyclic number.

It is not a de Polignac number, because 6438721 - 2²¹ = 4341569 is a prime.

It is not a weakly prime, because it can be changed into another prime (6432721) 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, 3219360 + 3219361.

It is an arithmetic number, because the mean of its divisors is an integer number (3219361).

Almost surely, 2^6438721 is an apocalyptic number.

It is an amenable number.

6438721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6438721 is an equidigital number, since it uses as much as digits as its factorization.

6438721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8064, while the sum is 31.

The square root of 6438721 is about 2537.4634972744. The cubic root of 6438721 is about 186.0372319193.

The spelling of 6438721 in words is "six million, four hundred thirty-eight thousand, seven hundred twenty-one".