6439681 has 2 divisors, whose sum is σ = 6439682. Its totient is φ = 6439680.

The previous prime is 6439679. The next prime is 6439703. The reversal of 6439681 is 1869346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6426225 + 13456 = 2535^2 + 116^2 .

It is a cyclic number.

It is not a de Polignac number, because 6439681 - 2¹ = 6439679 is a prime.

It is a super-2 number, since 2×6439681² = 82938982763522, which contains 22 as substring.

Together with 6439679, it forms a pair of twin primes.

It is a Chen prime.

6439681 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 6439681.

It is not a weakly prime, because it can be changed into another prime (6431681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3219840 + 3219841.

It is an arithmetic number, because the mean of its divisors is an integer number (3219841).

Almost surely, 2^6439681 is an apocalyptic number.

It is an amenable number.

6439681 is a deficient number, since it is larger than the sum of its proper divisors (1).

6439681 is an equidigital number, since it uses as much as digits as its factorization.

6439681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 37.

The square root of 6439681 is about 2537.6526555067. The cubic root of 6439681 is about 186.0464773821.

The spelling of 6439681 in words is "six million, four hundred thirty-nine thousand, six hundred eighty-one".