639947 has 8 divisors (see below), whose sum is σ = 797952. Its totient is φ = 498600.

The previous prime is 639941. The next prime is 639949. The reversal of 639947 is 749936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639947 - 2¹⁰ = 638923 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 639947.

It is not an unprimeable number, because it can be changed into a prime (639941) 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 in 7 ways as a sum of consecutive naturals, for example, 4079 + ... + 4232.

It is an arithmetic number, because the mean of its divisors is an integer number (99744).

2⁶³⁹⁹⁴⁷ is an apocalyptic number.

639947 is a deficient number, since it is larger than the sum of its proper divisors (158005).

639947 is a wasteful number, since it uses less digits than its factorization.

639947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8329.

The product of its digits is 40824, while the sum is 38.

The square root of 639947 is about 799.9668743142. The cubic root of 639947 is about 86.1750086806.

It can be divided in two parts, 6399 and 47, that added together give a palindrome (6446).

The spelling of 639947 in words is "six hundred thirty-nine thousand, nine hundred forty-seven".