639647 has 2 divisors, whose sum is σ = 639648. Its totient is φ = 639646.

The previous prime is 639637. The next prime is 639671. The reversal of 639647 is 746936.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 639647 - 2⁴ = 639631 is a prime.

It is a Chen prime.

It is a d-powerful number, because it can be written as 6² + 3¹² + 6⁶ + 9⁵ + 4³ + 7⁴ .

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639647.

It is not a weakly prime, because it can be changed into another prime (639637) 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, 319823 + 319824.

It is an arithmetic number, because the mean of its divisors is an integer number (319824).

2⁶³⁹⁶⁴⁷ is an apocalyptic number.

639647 is the 428-th centered heptagonal number.

639647 is a deficient number, since it is larger than the sum of its proper divisors (1).

639647 is an equidigital number, since it uses as much as digits as its factorization.

639647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 35.

The square root of 639647 is about 799.7793445695. The cubic root of 639647 is about 86.1615406156.

The spelling of 639647 in words is "six hundred thirty-nine thousand, six hundred forty-seven".